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Transcript
Quark Matter 2006 Abstract Administration
Quark Matter 2006 Conf. - November 14-20, 2006, Shanghai - P. R. China
I. Global and Collective Dynamics in A+A Collisions
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
A Statistical model analysis of yields and fluctuations at SPS and RHIC energies
P8
Effect of equilibrium phase transition on multiphase transport in relativistic heavy ion collisions
P8
BJORKEN EXPANSION WITH GRADUAL FREEZE OUT
P8
ENERGY DEPENDENCE OF ELLIPTIC FLOW WITHIN A TRANSPORT APPROACH
P9
Fluid Dynamics as Diagnostic Tool for Heavy Ion Collisions
P9
New Formulation of Dissipative Relativistic Hydrodynamics: A minimal theory
P10
Transport model analysis of particle correlations in relativistic heavy ion collisions at femtometer scales P10
On a “microscopic Hubble constant” from relativistic nuclear collisions
P11
SYSTEM SIZE DEPENDENCE OF FREEZE-OUT PROPERTIES AT RHIC
P11
Anisotropic flows and their scaling in relativistic heavy ion collisions
P12
KINK IN NUCLEAR PHASE DIAGRAM - A SIGNAL OF PHASE TRANSITION?
P12
Global Characterization of Heavy Ion Collisions with the CMS Experiment at the LHC
P13
P13
ON THE NECESSITY TO INCLUDE EVENT-BY-EVENT FLUCTUATIONS IN EXPERIMENTAL
EVALUATION OF ELLIPTICAL FLOW
P14
ON THE STRONGLY-INTERACTING LOW-VISCOSITY MATTER CREATED IN RELATIVISTIC
NUCLEAR COLLISIONS
P14
Heat capacity and average transverse momentum relevant to QGP phase transition
P15
Understanding the initial state eccentricity in AA collisions
P15
Jet Tomographic Tests of the CGC Initial State at RHIC and LHC
P16
Identify Bottom Contribution in Non-photonic Electron Spectra and v2 from Au+Au Collisions at RHIC P16
s
NN
20. Rapidity Dependency of Coalescence in Au+Au Collisions at
=200 GeV.
P17
21. TWO-CHARGED-PARTICLE AZIMUTHAL ANGLE CORRELATION AS ANOTHER PRESENTATION
OF ANISOTROPIC ELLIPTIC FLOW IN RELATIVISTIC HEAVY ION COLLISIONS
P17
22. ANISOTROPIC FLOW AT RHIC: HOW UNIQUE IS THE NUMBER-OF-CONSTITUENT-QUARK
SCALLING ?
P17
23. Nuclear Stopping: Paving the way from RHIC to LHC
P18
24. Hadron pTspectra and blast-wave description of In-In collisions at the CERN SPS.
P18
25. Simulations of Elliptic Flow in Heavy-Ion Collisions with the CMS Experiment at the LHC
P19
26. Low pT Hadronic Physics with the CMS Detector at the LHC
P19
27. ENERGY CONSERVATION IN RELATIVISTIC HEAVY-ION COLLISIONS
P19
28. Anti-particle to particle ratios in p+p, d+Au, Cu+Cu and Au+Au collisions at RHIC
P20
29. Multiparticle production to next-to-leading order in AA collisions
P21
Forward nuclear modification factor in Au-Au and Cu-Cu collisions at s =62.4GeV
P21
PARTICLE EMISSION FROM COLLISION SPECTATORS
P22
Source Imaging of pion emission sources in Pb+Pb collisions at SPS energies
P23
Counting valence quarks at RHIC and LHC.
P23
System size and energy dependence of charged-particle multiplicity distributions in p+p, d+Au, Cu+Cu and
Au+Au collisions at RHIC.
P23
35. Source chaoticity in relativistic heavy collisions at SPS and RHIC
P24
30.
31.
32.
33.
34.
s
NN
36. Centrality Dependence of Charged Hadron p_t Spectra at Forward Rapidities in CuCu Collisions at
=
200GeV
P24
37. GLOBAL POLARIZATION OF QGP IN NON-CENTRAL AA COLLISIONS AT HIGH ENERGIES
P25
38. PION ELLIPTIC FLOWS AND HBT INTERFEROMETRY IN A GRANULAR QUARK-GLUON
PLASMA DROPLET MODEL
P26
39. THE EFFECT OF THE SPECTATOR CHARGE ON THE CHARGED PION SPECTRA IN PERIPHERAL
ULTRARELATIVISTIC HEAVY-ION COLLISIONS
P26
40. Rapidity and pT Dependence of Identified-Particle Elliptic Flow at RHIC
P27
1
41. Why even a small viscosity matters at RHIC
P27
42. System size and rapidity dependence of the nuclear modification factor
P28
43. Energy and Centrality Dependence of Directed and Elliptic Flow in Cu+Cu and Au+Au Collisions at RHIC
Energies
P28
44. Yields and elliptic flow of $d(\overline{d})$ and $^{3}\!He(^{3}\overline{He})$ in Au+Au collisions at
$\sqrt{s_{_{NN}}}$ = 200 GeV
P28
45. INCIDENT-ENERGY AND SYSTEM-SIZE DEPENDENCE OF DIRECTED FLOW
P29
46. The inclusive photon and charged particle $v_2$ at $\sqrt{s_{NN}}=$200GeV in Au+Au and Cu+Cu
collisions
P29
47. PHENIX MEASUREMENTS OF REACTION PLANE DEPENDENCE OF HIGH PT PHOTONS AND
PIONS IN Au+Au COLLISIONS
P30
48. v2 & v4 centrality, pt and particle-type dependence in Au+Au collisions at RHIC
P30
49. High-pT Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX
P31
50.
51.
52.
53.
54.
55.
s
NN
Spin alignment of vector mesons (k*0,φ) in Au+Au and p+p collisions at
= 200 GeV
Excitation functions of baryon anomaly and freeze-out properties at RHIC-PHENIX
Energy and system size dependence of photon production at forward rapidities at RHIC
PHENIX Studies of the Scaling Properties of Elliptic Flow at RHIC Energies
Global polarization of Lambda hyperons in Au+Au collisions at RHIC
Energy and system size dependence of elliptic flow and v2/ε scaling
P31
P31
P32
P32
P33
P33
II. Jet Quenching and Medium Modification of Jet Particles
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
Large p/π ratios at RHIC and LHC
P33
Mach cones and dijets-angular correlations as a probe of early medium evolution
P34
DOES THE CRONIN PEAK DISAPPEAR?
P34
ARE JETS QUENCHED IN COLD NUCLEI?
P35
ENERGY LOSS OF HIGH ENERGY PARTONS IN HOT QGP AND HIGH PT PHOTONS
P35
Calculation of Hard Probe - Medium Interactions in 3D-Hydrodynamics
P36
Quark and gluon jet conversions in the quark-gluon plasma
P36
Parton Energy Loss at Twist-Six in Deeply Inelastic e-A Scattering
P37
Parton Thermalization and EnergyLoss in ultrarelativistic Heavy Ion Collisions within a Parton Cascade P37
Heavy Flavor Physics at RHIC and LHC
P38
Simulation of jet quenching observables in Heavy Ion Collisions at the LHC
P38
IDENTIFIED PARTICLE NUCLEAR MODIFICATION FACTORS AT RAPIDITY 2 - 3.8 IN AU+AU
COLLISIONS AT
=200 GEV
P39
68. SPATIO-TEMPORAL IMAGING OF THE QUARK GLUON PLASMA VIA JET MODIFICATION
P39
69. Hadron Suppression and Nuclear kT Enhancement studied with neutral pions from p+C, p+Pb, and Pb+Pb
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
Collisions at
=17.2 GeV
P40
Study of Jets in Heavy Ion Collisions with the CMS detector at the LHC
P40
Probing the Quark Gluon Plasma at LHC with virtual γ/Z0 tagged Jets in CMS
P41
ENERGY LOSS OF A HEAVY QUARK PRODUCED IN AFINITE SIZE MEDIUM
P41
HEAVY QUARK ENERGY LOSS DUE TO THREE-BODY SCATTERING IN A QUARK-GLUON
PLASMA
P41
Jet energy loss at RHIC and LHC, including collisional and radiative mechanisms and fluctuations
P42
Heavy quark energy loss and the non-photonic electron spectrum
P42
JET SHAPES IN OPAQUE MEDIA
P43
Can collisional energy loss explain nuclear suppression factor for light hadrons
P43
A Next-to-Leading-Order Analysis of Jet Quenching in High Energy A + A Collisions
P43
ALTERNATIVE VIEW ON JET ABSORPTION CENARIO
P44
Finite Creation Time Effects on Collisional Energy Loss of Non-Asymptotic Jets in a QGP
P45
Effect of jet quenching on the hydrodynamical evolution of QGP
P45
JETS IN HEAVY ION COLLISIONS WITH A FAST KT JET-FINDER
P46
NUMERICAL EVALUATION OF JET ENERGY LOSS
P46
A model of jet quenching in ultrarelativistic heavy ion collisions and high-pt hadron spectra at RHIC
P47
The QCD collisional energy loss revised
P47
Flow Coefficients and Jet Characteristics in Heavy Ion Collisions
P48
The fate of the Mach cone in covariant transport theory
P48
2
88.
89.
90.
91.
AdS/CFT and physics of heavy ion collisions
P48
Near-side $\Delta \eta$ correlations of high-pt hadrons from STAR
P49
Mechanism of Particle Production in p+p and d+Au collisions
P49
Properties of particle production at large transverse momenta in Cu+Cu and Au+Au collisions at RHIC
energies
P50
92. NUCLEAR-INDUCED PARTICLE SUPPRESSION AT LARGE xF AT RHIC
P50
s
NN
93. Low- and intermediate-pT azimuthal di-hadron correlations from
= 200GeV AuAu collisions
measured in STAR.
P51
94. Diagnosing energy loss: PHENIX results on high-pT hadron spectra
P51
95. Study of Parton-Medium Interactions via Two- Three- Particle Jet Correlations in PHENIX
P52
III. Strangeness and Heavy Flavor Production
96. Charm-hadron Correlations as a Sensitive Probe for Thermalizationin High-Energy Nuclear Collisions P52
97. Competition Between J/ψ Suppression and Regeneration in Quark-Gluon Plasma
P53
98. Cold Nuclear Matter Effects on J/ Production in p+A, d+Au and A+A Collisions
P53
99. Production of strange particles at RHIC via quark recombination
P53
100. Status ond Comparison of Chemical Freeze-Out Criteria
P54
101. Strangeness production in Au+Au reactions at 62.4 AGeV
P55
102. CENTRALITY AND ENERGY DEPENDENCE OF MESON, PROTON AND HYPERON PRODUCTION
P55
103. PRODUCTION OF Φ MESON IN GOLD-GOLD AND P+P COLLISIONS AT TOP RHIC ENERGY P55
104. DOES CHEMICAL EQUILIBRIUM OCCUR WITHIN SMALL CLUSTERS
P56
s
NN =5.5TeV
105. Energy loss of charm quark via dimuon production in Pb-Pb collisions at
P56
106. CERES measurement of strangeness production in central Pb-Au collisions at top SPS energy
P57
107. Charm Quark Thermalization in Quark-Gluon Plasma
P57
108. ALICE potential for open heavy-flavour physics
P57
109. STRANGE PARTICLE PRODUCTION AND THEIR CORRELATIONS IN DIS AT HERA
P58
110. Quarkonium Production in Heavy-Ion Collisions with CMS Experiment at the LHC
P58
111. First results on J/ψ production in p-A collisions at 158 AGeV
P58
112. NA60 results on J/ψ suppression in In-In collisions at 158 AGeV
P59
113. Heavy Quark measurements with the Forward Silicon Vertex Tracker upgrade for PHENIX
P59
114. The Centrality Dependence of Strange Baryon and Meson Production in Cu+Cu and Au+Au Relativistic
s
NN = 200 GeV
Heavy Ion Collisions with
P60
P60
116. High pT azimuthal and pseudorapidity correlations with strange baryons and mesons at RHIC
P61
117. STATISTICAL HADRONIZATION OF HEAVY QUARKS IN NUCLEUS-NUCLEUS COLLISIONS P61
118. Thermalization of Heavy Quarks and Consequenceson Non-photonic e- p┴ Spectra
P62
119. J/ψ PRODUCTION FROM CHARM COALESCENCE IN RELATIVISTIC HEAVY ION COLLISIONSP62
120. J/ψ production relative to the reaction plane in Pb-Pb collisions at the CERN SPS
P62
121. Heavy flavor production in pA collisions within the MV+BK framework
P63
122. Charm Quark Energy Loss in Dense Matter within the Light-Cone Path Integral Approach
P63
123. HEAVY QUARK ENERGY LOSS THROUGH SOFT QCD SCATTERING IN THE QGP
P64
124. Heavy Quark Diffusion in N=4 Yang-Mills at Strong Coupling
P64
125. Charm-anticharm azimuthal correlations at RHIC
P65
126. Heavy Quarkonium Survival in Quark-Gluon Plasma
P65
127. Study $B$ and $D$ Contributions via Azimuthal Correlations between Non-Photonic Electrons and Charged
P65
128.  Production at RHIC: Characterization of Coexistence Phase
P66
129. K*(892) production in Au-Au collisions at RHIC
P66
130. Search for Exotic Multi-quark Resonances in Relativistic Nuclear Collisions
P66
131. OPEN CHARM RECONSTRUCTION IN ALICE: D+ → K −π+π+
P66
132. Non-photonic electron yields from Cu+Cu collisions at $\sqrt{s_{NN}} = 200$ GeV at STAR.
P67
133. Centrality dependence of J/ψ production in Au+Au and Cu+Cu collisions by the PHENIX Experiment at
RHIC
P67
134. Measurement of leptonic and hadronic decays of ω and φ mesons at RHIC by PHENIX
P68
3
135. Scaling of charm integrated cross section and modification of its transverse momentum spectra in d+Au and
Au+Au collisions at RHIC
P68
136. Heavy Quarkonia Production in p+p collisions from the PHENIX Experiment
P68
137. Ξ0(1530) Production in Heavy-Ion Collisions and its Implications for ∆ttherm-chem
P69
138. HEAVY QUARK MODIFICATION IN A COMBINED TRANSPORT+QUENCHING APPROACH
P70
139. PHENIX results for J/ψ transverse momentum and rapidity dependence in Au+Au and Cu+Cu collisions P70
140. Heavy Quark Measurements by Single Electrons in the PHENIX Experiment
P70
141.
A d+Au data-driven prediction of cold nuclear matter effects on J/ψ production in Au+Au collisions at
RHIC
P71
142.
A measurement of the centrality dependence of the NΩ/Nφ ratio and φ anisotropic flow - a test of
thermalization in Au+Au collisions at RHIC
P71
143.
Transverse momentum broadening of heavy quarkonium production
P71
144.
Quarkonium Production in STAR
P72
145.
Elliptic flow of electron from heavy flavor decay by the PHENIX
P72
IV.Direct Photons, Dileptons and Vector Mesons
146.
ELECTROMAGNETIC RADIATION FROM BROKEN SYMMETRIES IN RELATIVISTIC
NUCLEAR COLLISIONS
P73
147.
Thermal Radiation from Au + Au Collisions at s =200 GeV/A Energy
P73
148.
Thermal Dimuon Yields at NA60
P73
149.
THEORETICAL INTERPRETATION OF RECENT SPS DILEPTON DATA
P74
150.
DIELECTRON PRODUCTION IN C+C COLLISIONS WITH HADES
P74
151.
What does the ρ-meson do? NA60's dimuon experiment and in-medium modification of vector mesons
P76
152.
Measuring Photons and Neutrons at Zero Degree in CMS
P76
153.
NA60 results on charm and intermediate mass dimuons production in In-In 158 GeV collisions
P77
154.
New results on the ρ spectral function in Indium-Indium collisions
P77
155.
Photon-tagged correlations from RHIC to LHC
P77
156.
HIGH MOMENTUM DILEPTON PRODUCTION FROM JETS IN A QUARK-GLUON PLASMAP78
157.
Direct photon production at both initial partonic and final hadronic states in p+p and Au+Au collisions
at top RHIC energy
P78
158.
Thermal Dilepton Production from Dropping ρ based on the Vector Manifestation
P79
159.
Improved Quark Mass Density-dependant model with quark and ω, σ meson couplings and the
deconfinement phase transition of nuclear matter
P79
160.
MEDIUM MODIFICATION ON VECTOR MESONS IN 12 GeV p + A REACTIONS
P80
161.
Vector meson spectral function in asymmetric nuclear matter
P80
162.
Low mass dielectron measurements at J-PARC
P81
163.
PARTON TRANSVERSE MOMENTA AND DIRECT PHOTON PRODUCTION IN HADRONIC
COLLISIONS
P81
164.
Observation of ∆φ∆η Scaled Correlation Signals which increase with Centrality of Au Au collisions
at sNN =200 Gev
P82
165.
First Measurements of Elliptic Flow Fluctuations
P82
166.
Is There A Mach Cone? – Three-Particle Azimuthal Correlations from STAR
P83
167.
Dielectron continuum measurements in √sNN=200 GeV Au+Au and Cu+Cu collisions at PHENIX P83
168.
Systematic Study of High-pT Direct Photon Production with the PHENIX Experiment at RHIC
P83
169.
A systematic study of low and medium pT direct photon production in the PHENIX experiment
P84
170.
Azimuthal γ-charged-hadron correlations in d+Au and p+p collisions from STAR at √sNN = 200 GeV
P84
171.
172.
173.
174.
175.
176.
Fluctuations, Correlations And Finite Volume Effects in HIC
Study of non-thermal phase transition in relativistic nuclear collisions
From Di-hadron correlations to parton intrinsic transverse momentum
Event-by-event pT uctuations and multiparticle clusters in relativistic collisions
Characteristic form of boost-invariant and cylindrically non-symmetric hydrodynamic equations
Femtoscopy in Hydrodynamics Inspired Models with Single Freeze-out
4
P84
P85
P86
P86
P87
P87
177.
178.
179.
180.
181.
182.
183.
Scale Dependence of Mean Transverse Momentum Fluctuations at Top SPS Energy
P88
New Results on Fluctuations and Correlations From the 49Na Experiments
P88
Resonance production in Heavy Ion Collisions at RHIC (what is strange and what is not so strange?P89
Elliptic flow fluctuations in 200 GeV Au+Au collisions at RHIC
P89
Two-particle angular correlations in pp, dA and AA collisions at PHOBOS
P90
Methods for Jet Studies with Three-Particle Correlations
P90
Two- and three particle azimuthal correlations of high-pt charged hadrons in Pb-Au collisions at 158
AGeV beam energy.
P91
184.
Multiplicity fluctuations in Cu+Cu and Au+Au collisions at RHIC
P91
185.
An Inverson-Asymmetric Source Function for HBT Analysis in Relativistic Heavy Ion Collisions P91
186.
Detecting QGP With Charge Transfer Fluctuations
P92
187.
New Observable Predictions from Elastic, Inelastic, and Path Length Fluctuating Energy Loss
P93
188.
Charge fluctuations and signals of QGP phase transition
P93
189.
P93
190.
New results on pion-pion and pion-proton correlations from the CERES Pb+Au run at 158 GeV per
nucleon
P94
191.
Measuring Shear Viscosity Using Transverse Momentum Correlations
P94
192.
Parametrization of Bose-Einstein Correlations and Reconstruction of the Source Function in Hadronic
Z-Boson Decays Using Tth L3 Detector
P94
193.
Eccentricity Fluctuations and Elliptic Flow at RHIC
P95
194.
Particle production and correlation in ep collisionson behalf of the H1 and ZEUS collaborationsa P95
195.
Energy-Energy Correlations and Other Di-Jet/Jet-Photon Correlations in PHENIX
P95
196.
Gluon Transverse Momenta and Heavy Quark-Antiquark Pair Production and Correlations in Hadronic
Collisions at High Energy
P96
197.
A Method For Measuring Elliptic Flow Fluctioins with 1st-order Event Planes
P96
198.
Two- and Three-particle Correlations in a Partonic Transport Model
P97
199.
TWO-PARTICLE CORRELATION IN HEAVY-ION COLLISIONS AT CSR ENERGY
P97
200.
PROTON FEMTOSCOPY IN STAR
P97
201.
Methods for Measuring Elliptic Flow Fluctuations
P98
202.
200 GeV Au+Au and Cu+Cu Collisions
P98
Probing the nature of the long-range structure observed in the pion emission source at RHIC-PHENIX
P99
204.
Suppression of Statistical Background in Event-Structure Analysis Using Factorial Moments
P99
205.
Understanding the Particle Production Mechanism with Correlation Studies Using Long and Short
Range Correlations and the Balance Function.
P100
206.
Net charge fluctuations using higher order cumulants
P100
207.
What do PHENIX measurements of jet mediated identified particle correlations tell us about the sQGP
at RHIC?
P101
208.
Identification of Mach-Cone Using Three-Particle Jet-Like Correlations
P101
209.
Search for a critical behavior by measuring spatial correlation lengths via multiplicity density
fluctuations at RHIC-PHENIX
P102
210.
mT and centrality scaling properties of source size and duration time measured by Bose-Einstein
correlations at RHIC-PHENIX
P102
211.
Identical Meson Interferometry in STAR Experiment
P103
212.
Scaling Properties of Fluctuation Measurements from PHENIX
P103
203.
VI.QCD at High Temperature and Density
213.
214.
215.
216.
Quark mass thresholds in QCD thermodynamics
P104
Neutrino processes in normal and color superconducting quark matter
P104
Pion-Pion-Sigma Mixing in Pion Superfluidity
P105
Mesonic correlation functions at finite temperature and density in the Nambu – Jona - Lasinio model
with a Polyakov loop
P105
217.
Gloun fluctuation-induced first order transition and the complex energy gap in high density QCD P105
218.
Viscosity in the strongly interacting quark matter around the critical temperature
P106
219.
THE FREE ENERGY OF STATIC QUARKS IN FULL QCD
P106
220.
Static quark free energies at finite temperature in full QCD lattice simulations
P106
221.
Further Analysis of Collective Excitations of Quarks at Finite Temperature
P107
5
222.
223.
224.
225.
226.
227.
POLYAKOV LOOP IN CHIRAL QUARK MODELS AT FINITE TEMPERATURE
P108
DIMENSION TWO GLUON CONDENSATES AND THE HEAVY QUARK FREE ENERGY P109
The transition temperature in QCD with physical light and strange quark masses
P109
A field theoretical model for QCD thermodynamics
P110
Simulation of the transition between meson-system and QGP in a transport model
P110
Thermodynamics of two-flavor lattice QCD with an improved Wilson quark action at non-zero
temperature and density
P111
228.
LANDAU POTENTIAL STUDY OF THE CHIRAL PHASE TRANSITION IN A QCD-LIKE
THEORY
P111
229.
DYNAMICS IN EVOLUTION OF BULK QCD MATTER AT RHIC
P112
230.
Unified description of deconfined QCD equation of state
P112
231.
Qurak Spectrum above the critical Temperature from the Schwinger-Dyson Equation
P113
232.
Phase diagram at finite temperature and quark density in the strong coupling limit of lattice QCD for
color SU(3)
P113
233.
Nucleon-Nucleon Potential from Lattice QCD
P114
234.
Hadron-quark continuity induced by the axial anomaly in dense QCD
P115
VII. Low-x Parton Dynamics and Parton Saturation
235.
236.
237.
238.
239.
Are there monojets in high-energy proton-nucleus collisions?
Energy dependence of nuclear suppression in the fragmentation region
P116
P116
QQ  production in pA collisions at RHIC and the LHC
P116
Identified hadron production in d+Au and p+p collisions at RHIC
P117
Probing small-x gluons and large-x quarks: jet-like correlations between forward- and mid-rapidity in pp,
d+Au, and Au+Au collisions from STAR
P117
240.
Nuclear modification to parton evolution and onset of parton saturation
P118
VIII. Quark Matter in Astro-particle Physics
241.
242.
243.
244.
245.
246.
Phase Diagram of Color Superconductivity with Spin-0 and Spin-1 Pairings
Neutral Dense Quark Matter at Intermediate Temperatures
Hyperon-Quark Mixed Phase in Compact Stars
Black Hole Formation during the QCD Phase Trasition in the early Universe
Two step conversion of Neutron star to Strange star
Modern quark matter equations of state vs. compact star observations
P118
P119
P119
P120
P120
P121
IX.New Theoretical Developments
247.
248.
249.
250.
251.
252.
253.
254.
255.
256.
257.
Thermalization of Quark-Gluon Matter
Micro-canonical pentaquark production in e+e- annihilations and pp collisions
BOUND QUARKONIA IN QUARK-GLUON PLASMA
Susceptibilities and the Phase Structure of a Chiral Model with the Polyakov Loop1
Dissipative hydrodynamics in 2+1 dimensions
CHROMO-HYDRODYNAMICS OF THE UNSTABLE QUARK-GLUON PLASMA
QGP correlations and phases of many-particle amplitudes
The Statistical Model and Different Freeze-Out Conditions
EARLY TIME EVOLUTION OF HIGH ENERGY HEAVY ION COLLISIONS
What can we learn from the AdS/CFT correspondence about heavy ion phenomenology?
SPACE-TIME EVOLUTION OF A CHEMICALLY EQUILIBRATING QGP AT FINITE
DENSITY
258.
Amplification of Quantum Meson Modes in the Late Time of the Chiral Phase Transition
259.
MAGNETIC INSTABILITY OF QUARK MATTER
260.
Oscillating Correlation Function in QGP
261.
Jet-fluid string formation and decay in high-energy heavy-ion collisions
262.
Analysis of large transverse momentum distributions by relativistic diffusion model
263. Unconventional color superconductor: beyond standard BCS theory
264. HYPERON POLARIZATION IN QUARK-DIQUARK CASCADE MODEL
6
P121
P122
P122
P123
P124
P124
P124
P125
P125
P125
BARYON
P126
P126
P127
P128
P128
P129
P129
P130
265. A CALCULATION OF TRANSPORT COEFFICIENTS OF RELATIVISTIC DISSIPATIVE
P130
266. ELECTROMAGNETIC RADIATION FROM BROKEN SYMMETRIES IN RELATIVISTIC NUCLEAR
COLLISIONS
P131
267. JET-PLASMA INTERACTIONS AND THEIR ELECTROMAGNETIC SIGNATURE
P131
268. All orders Boltzmann collision term from the multiple scattering expansion of self-energy
P132
269. Collective excitations of quarks near chiral transition at finite temperature
P132
270. From RHIC to LHC: A relativistic diffusion approach
P132
271. QUARK-QUARK DOUBLE SCATTERING IN NUCLEI WITH TWIST-EXPANSION APPROACH P133
272. DECIPHERING THE PROPERTIES OF THE MEDIUM PRODUCED IN HEAVY ION COLLISIONS AT
RHIC BY A pQCD ANALYSIS OF QUENCHED LARGE p⊥ PION SPECTRA
P134
273. QUARKONIA CORRELATORS AND SPECTRAL FUNCTIONS
P134
274. PION NUCLEON INTERACTION IN A LINEAR SIGMA MODEL WITH HIDDEN GAUGE
SYMMETRY
P135
275. ANOMALOUS VISCOSITY OF AN EXPANDING QUARK-GLUON PLASMA
P135
276. FORGOTTEN NUCLEAR EFFECTS IN HIGH-ENERGY HEAVY-ION COLLISIONS
P135
277. Spectrum of soft mode with thermal mass of quarks above critical temperature
P136
278. Shear viscosity in weakly coupled N=4 Super Yang-Mills
P136
X. Future Experiments and Facilities
279. Trigger Decision Criterion of the ALICE Photon Spectrometer
P137
280. The Laser of the ALICE's Time Projection Chamber
P137
281. The CBM experiment at FAIR -planning for an investigation of the intermediate range of the QCD phase
diagram–
P138
282. PERFORMANCE OF FORWARD RESISTIVE PLATE CHAMBERS FOR MUON TRIGGERING AT
CMS/LHC
P138
283. The Time of Flight detector of the ALICE experiment
P139
284. The ALICE Forward Multiplicity Detector and Readout
P139
285. Proton-proton physics with the ALICE muon spectrometer at the LHC
P140
286. Probing partonic distribution functions in nucleons and nucleus with Forward Calorimeters in the PHENIX
experiment at RHIC
P140
287. Progress of ALICE-PHOS Detector at LHC
P141
288. PROBABILISTIC HEAVY ION JET RECONSTRUCTION FOR RHIC AND LHC
P141
289. Low-x QCD with CMS at CERN-LHC
P142
290. Electronics performance of the calorimeter PHOS
P142
291. RELATIVISTIC HEAVY ION COLLIDER (RHIC) ACCELERATOR FACILITY: PRESENT AND
FUTURE
P142
292. High Level Trigger applications for the ALICE experiment
P143
293. Detector Construction Database for ALICE Experiment
P143
294. Quarkonia Detection in the ALICE Experiment
P144
295. Proton-proton Physics in ALICE
P144
296. Equation of State Study in U+U collisions at CSR
P145
297. The Inner Tracking system of ALICE
P145
298. Heavy-Ion Physics with the CMS detector at the LHC
P146
299. Minimum Bias and Underlying event measurement with CMS detector from startup
P146
300. Triggering on Hard Probes in Heavy-Ion Collisions with the CMS Experiment at the LHC
P147
301. Exotic physics at the LHC with CASTOR in CMS
P147
302. A Zero Degree Calorimeter for the ATLAS Experiment
P148
303. New results and perspectives on RAA measurements below 20 GeV CM-energy at fixed target machines P148
304. RESULTS FROM THE ALICE TEST TPC
P148
305. STUDY OF HADRONIC RESONANCES IN ALICE
P149
306. "Heavy-Ion Physics with the ATLAS Detector at the LHC"
P149
307. DETECTOR EFFICIENCY EVALUATION USING DEAD ZONE REMOVAL BY FIDUCIAL CUTS P150
308. A Study of the Intrinsic Time Resolution of MRPC Used in STAR-TOF
P150
309. A barrel TOF for STAR at RHIC
P150
310. CONSTRUCTION AND EXPECTED PERFORMANCE OF THE HADRON BLIND DETECTOR FOR
THE PHENIX EXPERIMENT AT RHIC
P151
311. A Heavy Flavor Tracker for STAR
P151
312. COMMISSIONING OF THE ALICE TPC
P151
7
I. Global and Collective Dynamics in A+A Collisions
1.
A Statistical model analysis of yields and fluctuations at SPS and RHIC energies
G. Torrieri
Department of Physics, McGill University, Montreal, Quebec, Canada
Johann Wolfgang Goethe University, Frankfurt am Main, Germany, [email protected]
It was recently shown [1] that an analysis combining yield and fluctuation observables can
tightly constrain the freeze-out temperature, degree of chemical equilibration, and post-freeze out
interactions [2] in heavy ion collisions. Preliminary analyses using this technique have already been
used to analyze RHIC data [2]; Moreover, an open-source program with the capability of fitting
both yields and fluctuations has recently been published [3].
In this presentation, we extend this analysis to SPS data, with a view of studying
event-by-event fluctuations of K/π and p/π ratios, together with particle yields (π,K,p, hyperons and
anti-particles) for a range of energies. We will describe the energy dependence of both the best fit
parameters, and the fit quality, defined as the ability of the statistical model to fit both yields and
fluctuations with the same thermal parameters.
We discuss our results in view of the observed sharp energy dependence of some soft
observables at SPS (the so-called kink'', horn'',''step'' [4]). In particular, we examine the proposed
explanations for these features in view of our analysis.
References:
[1] G. Torrieri, S. Jeon and J. Rafelski, ''Particle Yield Fluctuations And Chemical Non-Equilibrium At Rhic,''
Phys. Rev. C, in press arXiv:nucl-th/0503026.
[2] G. Torrieri, ''Resonances and fluctuations of strange particle in 200-GeV Au–Au collisions,'' J. Phys. G, in
press arXiv:nucl-th/0606009.
[3] G. Torrieri, S. Jeon, J. Letessier and J. Rafelski, Comput. Phys. Commun.,in press SHAREv2: Fluctuations
and a comprehensive treatment of decay feed-down,'' arXiv:nucl-th/0603026.
[4] M. Gazdzicki et al. [NA49 Collaboration], Report from NA49,J.Phys.G30,S701(2004) nucl-ex/0403023.
2.
Effect of equilibrium phase transition on multiphase transport
in relativistic heavy ion collisions
Yu Meiling, Du Jiaxin and Liu Lianshou
Institute of Particle Physics, Center China Normal University
Wuhan, 430079, P. R. China, [email protected]
The hadronization scheme for parton transport in relativistic heavy ion collisions is considered
in detail. It is pointed out that the traditional scheme for particles being freezed out one by one leads
to serious problem on unreasonable long lifetime for partons. In order to avoid this problem, we
assume the system to have reached global equilibrium and extract temperature from the system by
thermodynamics formula. As the decreasing of temperature the parton phase is allowed to hadronize
as a whole after a supercooling stage. It turns out that the modified model with a global phase
transition inherits the success of the original one in elliptic flow and is able to reproduce the
experimental longitudinal distributions of final state particles better than the original one does. The
encouraging results indicate that a relevant parton transport model for relativistic heavy ion
collision should take equilibrium phase transition into proper account.
References:
[1] T. Sawyer, M. Twain, and I.M. Yu, International Journal of Experimental Physics, v. 97, p. 229-256, 1994.
3.
BJORKEN EXPANSION WITH GRADUAL FREEZE OUT
V.K. Magas a , L.P. Csernai b and E.~Molnar b
Departament d'Estructura i Constituents de la Mat\'eria
b Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain,
[email protected]
b Theoretical and Energy Physics Unit, University of Bergen,Allegaten 55, 5007 Bergen, Norway
a
8
[email protected] and [email protected]
The freeze out of the expanding systems, created in relativistic heavy ion collisions, will be
discussed. We combine kinetic freeze out equations [1,2] with Bjorken type system expansion
into a unified model. Such a model is a more physical generalization of the earlier simplified
non-expanding freeze out model [3]. The important feature of the proposed scenario is that physical
freeze out is completely finished in a finite time, which can be varied from 0 (freeze out
hypersurface) to ∞. The dependence of the post freeze out distribution function on the freeze out
time will be studied. Model allows analytical analyses for the simplest systems such as pion and
baryon gas with small baryon chemical potential. We shall see that the basic freeze out features,
pointed out in the earlier works [1,2], are not smeared out by the expansion of the system. The
entropy evolution in such a scenario will be also discussed.
References:
References
[1] E. Molnar, L. P. Csernai, V. K. Magas, A. Nyiri, K.Tamosiunas, nucl-th/0503047, to appear in Phys. Rev. C.
[2] E. Molnar, L. P. Csernai, V. K. Magas, Zs. I. Lazar, A. Nyiri, K. Tamosiunas, nucl-th/0503048.
[3] V.K. Magas, A. Anderlik, Cs. Anderlik, L.P. Csernai, Eur. Phys. J. C 30 p. 255-261, 2003.
4.
ENERGY DEPENDENCE OF ELLIPTIC FLOW WITHIN A TRANSPORT APPROACH
H. Petersen a and M. Bleicher b
für Theoretische Physik, Johann Wolfgang Goethe-Universität
Max-von-Laue-Str. 1, D-60438 Frankfurt am Main, Germany [email protected]
bInstitut für Theoretische Physik, Johann Wolfgang Goethe-Universität
Max-von-Laue-Str. 1, D-60438 Frankfurt am Main, Germany [email protected]
aInstitut
Recent data from the NA49 experiment on directed and elliptic flow for Pb+Pb reactions at
CERN-SPS are compared to calculations with a hadron-string transport model, the Ultra-relativistic
Quantum Molecular Dynamics (UrQMD) model. The rapidity and transverse momentum
dependence of the directed and elliptic flow, i.e. v1 and v2 , are investigated. The flow results are
compared to data at three different centrality bins. Generally, a reasonable agreement between the
data and the calculations is found. Furthermore, the energy excitation functions of v1 and v2
from E beam =90A$~MeV to E cm =200A GeV are explored within the UrQMD framework and discussed in the context of the available data. It is found that, in the energy regime below E beam  10A GeV, the inclusion of nuclear potentials is necessary to describe the data. Above 40A GeV beam energy, the UrQMD model starts to underestimate the elliptic flow. Around the same energy the slope of the rapidity spectra of the proton directed flow develops negative values. This effect is known as the third flow component ("antiflow") and cannot be reproduced by the transport model. These differences can possibly be explained by assuming a phase transition from hadron gas to quark gluon plasma at about 40A GeV. References: [1] H. Petersen, Q. Li, X. Zhu, M. Bleicher, Directed and elliptic flow in heavy ion collisions at GSI-FAIR and CERN-SPS, submitted to Phys. Rev. C [2] Y. Lu, M. Bleicher, F. Liu, Z. Liu, H. Petersen, P. Sorensen, H. St¨ocker, N. Xu, X. Zhu, J. Phys. G: Nucl. Part. Phys., v. 32, p. 1121-1129, 2006. 5. Fluid Dynamics as Diagnostic Tool for Heavy Ion Collisions L.P. Csernaia,b, V.K. Magasc, E. Moln´ara, and D.D. Strottmand of Physics, University of Bergen, N-5007 Bergen, Norway, [email protected] bMTA-KFKI, Research Institute for Particle and Nuclear Physics 1525 Budapest 114., P.O.Box 49, Hungary c Departament d’Estructura i Constituents de la Mat´eria, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain dDepartamento de F´ısica Te´orica and IFIC Centro Mixto, Universidad de Valencia-CSIC, Institutos de Investigaci´on de Paterna, Apdo. correos 22085, 46071, Valencia, Spain aDepartment 9 Three dimensional fluid dynamics represents a special and sensitive tool to trace down the details of reaction mechanism of heavy ion reaction. Flow influences the single particle observables and two particle correlations, and these observables are modeled simultaneously. The observables are determined by all three stages of the reaction: pre equilibrium initial stage, fluid dynamical stage, and final hadronization and freeze out stage. We describe all these stages in realistic and detailed models, without simplifying the configuration by assuming additional symmetries in any of these stages. We predict rapidity dependent v1 and v2 parameters. This way we trace forward backward asymmetry, present initially in collisions of finite impact parameter, which is sensitive to the formation of initial state, e.g. to the field strength of initial chromo-magnetic fields. We test also the possibility of early, rapid freeze out, and its consequences to two particle correlation observables. In addition the scaling and fluctuation properties of the event by event flow measurements give information on transport properties of the plasma as well as on hadronization dynamics. 6. New Formulation of Dissipative Relativistic Hydrodynamics: A minimal theory T. Kodamaa, T. Koideb, G.S. Denicolc and Ph. Motad Instituto de Física, Universidade Federal do Rio de Janeiro,Rio de Janeiro, 21941_972, Brazil a [email protected] , [email protected] , [email protected] , [email protected] One of the most important questions to be clarified in the hydrodynamical approach to the relativistic heavy ion physics is that the effect of dissipative processes. However, relativistic dissipative hydrodynamics introduces several difficulties, both conceptual and technical. Among them the 14 filed theory formulated by Muller, Israel and Stewart has been considered standard approach[1]. But it is quite complex and involves many unknown parameters from the point of QCD dynamics so that this theory still defines its complete application to practical problems such as relativistic heavy ion reactions although several works have been done in this direction[2]. In this work, we propose an alternative approach to this question[3]. We show that the physical origin of the second order theories can easily be understood in terms of memory effects. The irreversible current modified by the memory effects becomes consisitent with causality and sum rules[4]. Based on this idea, we introduced the memory effect to the relativistic dissipative hydrodynamic of Landau. We introduce only one extra parameter, the relaxation time$\tau
_{relax},$in addition to the usual viscosity coefficients of the Navier-Stokes equation. The resulting equation becomes hyperbolic, and in the limit of vanishing relaxation time, it recovers the Landau theory[5]. A fundamental advantage of the present approach from the point of practical applications is that the viscous terms are explicity given by the proper time integral in the past of usual independent variables of ideal hydrodynamics, that is, the velocity fields and local thermodynamical quantities. Thus, the implementation of our method to the existing ideal hydrocodes is almost trivial, particularly to those based on the local Lagrangian coodinate system such as SPheRIO[6]. This formalism is applied to the Bjorken model and compare with the previous analysis. A discussion on the effects of viscosity and relaxation time on azimuthal flow parameter will be discussed. References [1] See for the review, I.Muller.Living Rev. Relativity, 2, (1999), 1. [Online Article] [2] A.K. Chaudhuri, nucl-th/0604014, U. Heinz, H. Song and A.K. Chaudhuri, Phys.Rev.C73:034904 (2006), A.Muronga and D.H. Rischke, nucl-th/0407114, A.Muronga, Phys.Rev.C69:034903,2004, Phys.Rev.Lett.88:062302,2002, R. Baier, P. Romatschke, U. A.Wiedemann, hep-ph/0602249, nucl-th/0604006. [3] T. Kodama, T. Koide, G.S.Denical and Ph.Mota, hep-ph/0606161. [4] T. Koide, Phys. Rev. E72, 026135 (2005), T. Koide, G. Krein and R. O. Ramos, Phys.Lett. B 636, 96 (2006). [5] L. Landau and E. M. Lifshitz, Fluid Mechanics, p. 500 Addison-Wesley, 1958. [6] Y. Hama, T. Kodama and O. Socolowski Jr., Braz. J. Phys. 35 (2005) 24. 7. Transport model analysis of particle correlations in relativistic heavy ion collisions at femtometer scales 10 M. Bleichera and Q. Lib für Theoretische Physik, Goethe Universität, Max von Laue Strasse 1 60438 Frankfurt am Main, Germany, [email protected] b Frankfurt Institut for Advanced (FIAS), Max von Laue Strasse 1 60438 Frankfurt am Main, Germany, [email protected] aInstitut The pion source as seen through Hanbury-Brown-Twiss (HBT) correlations at BNL Relativistic Heavy Ion Collider (RHIC) and CERN-SPS energies is investigated within the UrQMD approach. We find that the calculated transverse momentum, centrality, and system size dependence of the Pratt-HBT radii RL and RS are reasonably well in line with experimental data. This is in contradiction to earlier hydrodynamical predictions that suggest a prolonged life time of the fireball at SPS energies due to the onset of a mixed phase. The predicted RO values in central heavy ion collisions are larger as compared to experimental data. The corresponding quantity RO  RS2 of the pion emission source is somewhat larger than experimental estimates. We conclude that except for the highest RHIC energies, HBT radii follow the expectations from string-hadronic dynamics. References Q. Li, M. Bleicher and H. St¨ocker, Phys. Rev. C 73, 064908 (2006). 8. On a “microscopic Hubble constant” from relativistic nuclear collisions Alexandru JIPA, Călin BEŞLIU, Ion Sorin ZGURĂ, Oana RISTEA, Cătălin RISTEA, Amelia HORBUNIEV, Ionuţ ARSENE, Dănuţ ARGINTARU, Marius CĂLIN, Tiberiu EŞANU Atomic and Nuclear Physics Chair, Faculty of Physics, University of Bucharest, P.O.Box MG-11, RO-077125 Bucureşti-Măgurele, ROMANIA, [email protected] Using similarities between cosmological scenarios on the Universe evolution after “Big Bang” and the behaviour of the highly excited nuclear matter formed in relativistic nuclear collisions, immediately after collisions we try an estimation of a “microscopic Hubble arameter/constant” for the expansion rate in relativistic nuclear collisions, similar with the cosmological Hubble constant. Temporal connections between the evolution of the nuclear matter after impact and the Universe evolution after “Big Bang” are used. Different cosmological scenarios have been used for “Hubble parameter/constant” estimations. Comparisons among methods have been done. Experimental results on participants, fireball sizes (identical particle interferometry), densities, particle spectra and temperatures obtained in Au-Au and Cu-Cu collisions at RHIC BNL energies, by BRAHMS Collaboration, have been used for doing these estimations. A “Hubble scale” for temporal evolution can be obtained using other experimental results, at different energies. Satisfactory agreement with Buda-Lund model estimation have been obtained. The ratio between the “microscopic Hubble parameter/constant” and cosmological Hubble constant is of the same order of magnitude with the ratio of the strengths of the strong interaction and gravitational interaction. References [1]. BRAHMS Collaboration – Phys.Rev.Lett.90(2003)102301 [2]. BRAHMS Collaboration – Phys.Rev.Lett.91(2003)072305 [3]. BRAHMS Collaboration – Phys.Rev.Lett.93(2004)102301 [4]. BRAHMS Collaboration – Nucl.Phys.A757(2005)1-27 [5]. Oana Ristea – Ph.D. Thesis, Faculty of Physics, University of Bucharest, 2005 [6]. Ion Sorin ZGURĂ – Ph.D. Thesis, Faculty of Physics, University of Bucharest, 2005 [7]. Amelia Horbuniev – Ph.D. Thesis, Faculty of Physics, University of Bucharest, 2006 [8]. M.Csanad, T.Csorgo, B.Lorstad – Nucl.Phys.A742(2004)80-94 9. SYSTEM SIZE DEPENDENCE OF FREEZE-OUT PROPERTIES AT RHIC aDepartment O. Barannikovaa for the STAR Collaboration of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA, [email protected] Identified particle spectra in heavy-ion collisions at different center-of-mass energies provide a unique tool to explore the QCD phase diagram. Analysis of Cu+Cu data collected by the STAR 11 experiment extends the systematic studies of bulk properties by addressing the size dependence of freeze-out parameters at RHIC. Identified   , K  , p and p spectra and ratios from s NN = 62.4 and 200~GeV Cu+Cu collisions are studied with hydro-motivated blast-wave and statistical model frameworks in order to characterize the freeze-out properties of this system. The new Cu+Cu results, along with measurements from Au+Au and pp collisions, are used to discuss the freeze-out parameters as a function of collision energy, system size, centrality and inferred energy density. In addition, the data provide further insight into strangeness production. This multi-dimensional systematic study reveals the importance of the collision geometry. These studies further our understanding of the QCD phases and are an advance towards the proposed RHIC energy scan to locate the critical point. 10. Anisotropic flows and their scaling in relativistic heavy ion collisions Lie-Wen Chena and Che Ming Kob of Theoretical Physics, Shanghai Jiao Tong University, Shanghai 200240, P. R. China, [email protected] bCyclotron Institute and Physics Department, Texas A&M University, College Station, Texas 77843-3366, USA, [email protected] aInstitute Recent results from a multiphase transport (AMPT) model [1] on the elliptic flow v2 and higher-order anisotropic flow v4 of particles produced in Au+Au collisions at s =200AGeV at the Relativistic Heavy Ion Collider (RHIC) will be reported. For higher-order anisotropic flow v4 [2], it is nonnegligible for partons and satisfy the scaling relation v n ,q ( pT ) ～ v2n,/q2 ( pT ) , which leads naturally to the observed similar scaling relation among hadron anisotropic flows when the coalescence model is used to describe hadron production from the partonic matter [3]. Furthermore, based on a dynamical quark coalescence model that uses the quark phase-space information from the AMPT model within the string melting scenario and includes the quark structure of hadrons, the v2 and v4 of  mesons and  (      ) baryons in Au+Au collisions at RHIC are studied [4]. We have found that the elliptic flows of  mesons and  baryons follow approximately the valence quark number scaling. The valence quark number scaled elliptic flows of  mesons and  baryons deviate, however, significantly from the underlying v2 of strange and antistrange quarks. We have also found that the scaling relation of v4 ( pT ) ～ v 22 ( pT ) observed experimentally for charged hadrons is also satisfied by  mesons and  baryons. In addition, the dependence of parton v2 and v4 as well as their scaling relation on their number of collisions will also be discussed [5]. References [1] Z.W. Lin, C.M. Ko, B.A. Li, B. Zhang, and S. Pal, Phys. Rev. C 72, 064901 (2005) and references therein. [2] L.W. Chen, C.M. Ko, and Z.W. Lin, Phys. Rev. C 69, 031901(R) (2004). [3] P.F. Kolb, L.W. Chen, V. Greco, and C.M. Ko, Phys. Rev. C 69, 051901(R) (2004). [4] L.W. Chen and C.M. Ko, Phys. Rev. C 73, 044903 (2006). [5] L.W. Chen and C.M. Ko, to be published. 11. KINK IN NUCLEAR PHASE DIAGRAM - A SIGNAL OF PHASE TRANSITION? E. Zabrodin a, L. Bravina a, I. Arsene a , M.S. Nilsson a, K. Tywoniuk a J. Bleibel b, G. Burau b, A. Faessler b, C. Fuchs b M. Bleicher c, H. Stöcker c a Department of Physics, University of Oslo, N-0316 Oslo, Norway, [email protected] b Institute for Theoretical Physics, University of Tübingen, D-72076 Tübingen, Germany c Institute for Theoretical Physics, University of Frankfurt,D-60438 Frankfurt a.M., Germany The relaxation to chemical and thermal equilibrium in the central zone of relativistic heavy-ion collisions at energies from AGS to SPS is studied within the microscopic transport model. To decide 12 whether or not the equilibration takes place particle yields and energy spectra from the central cell (of fixed volume V=125 fm3) are compared to predictions of the statistical model. We found that kinetic, thermal, and chemical equilibration is nearly approached for the period of 10-18 fm/c [1]. Within this time the expansion of matter in the cell proceeds with constant entropy per baryon ratio. For the bombarding energies around 40 AGeV the system crosses the critical point in the T   B plane predicted by lattice QCD calculations [2]. Study of the relaxation process at early times in smaller central cells [3,4] helps us to find a characteristic kink in the T   B diagrams corresponding to beginning of the equilibrated phase. The kink is observed for all energies and is similar to that found in lattice QCD calculations along the lines of constant entropy per baryon. Its origin can be attributed to the transition from string-dominated medium to the state of already formed hadrons. References [1] L. Bravina, E. Zabrodin, et al., Physical Review C, v. 60, p. 024904-14, 1999. [2] Z. Fodor, S.D. Katz and K.K. Szabo, Physics Letters B, v. 568, p. 73-~77, 2003. [3] L. Bravina, I. Arsene, M.S. Nilsson, K. Tywoniuk and E. Zabrodin, Journal of Physics G, in press. [4] L. Bravina, et al., to be published\/. 12. Global Characterization of Heavy Ion Collisions with the CMS Experiment at the LHC Aneta Iordanova for the CMS Collaboration University of Illinois, Chicago, IL, USA E-mail [email protected] Measuring the global characteristics of heavy-ion collisions at the LHC will be an extremely important early result that will provide the underlying foundation in our study of partonic matter at very high energies. The systematic study of the particle multiplicities have provided insight into the bulk particle production which lead to restrictions of models that attempt to describe the data. This data will also provide global constraints on the system as evidenced through limiting fragmentation as well as the role of parton saturation and the color glass condensate. Equally important will be the ability to correctly characterize the heavy-ion collision to enable differential studies versus centrality and pseudorapidity. The CMS experiment at the LHC has a suite of detectors with a wide pseudorapidity coverage that are ideally suited to these global studies. This talk will discuss the relevance and importance of some of these global measurements and the ability of the CMS detector to meet the corresponding experimental challenges. 13. CGC, Full 3D Hydro, and Hadronic Cascade T.~Hirano a, U.~Heinz b, D.~Kharzeev c, R.~Lacey d, and Y.~Nara e a Institute of Physics, The University of Tokyo Komaba 3-8-1, Meguro, Tokyo 153-8902, Japan, [email protected] bDepartment of Physics, Ohio State University 191 West Woodruff Avenue, Columbus, OH 43210, USA, [email protected] cNuclear Theory Group, Physics Department, Brookhaven National Laboratory Upton, NY 11973-5000, USA, [email protected] dDepartment of Chemistry, SUNY Stony Brook Stony Brook, NY 11794-3400, USA, [email protected] eInstitute f\"ur Theoretische Physik, J.W.~Goethe-Universit\"at Max v.~Laue Str.~1, D-60438 Frankgurt, Germany, [email protected] We investigate, based on a hydrodynamic approach, how robust the conclusion of discovery for perfect fluid QGP at RHIC is. In hydrodynamic simulations, one needs to model (1) initial conditions for thermodynamical variables and flow velocities, (2) equations of state for the produced QCD matter, and (3) decoupling/freezeout prescription in the late stage. The conclusion was obtained essentially from a particular set of the above three models. So it is of prime importance to check whether the conclusion remains valid even by changing model assumptions in hydrodynamics. Hirano and Gyulassy carried out a systematic study [1] for the 13 effect of freezeout prescription on final observables such as pT distributions and elliptic flow parameters. It was emphasized in Ref.[1] that the hadronic dissipation plays a very important role in simultaneous reproduction of particle ratio, spectra, and elliptic flow around midrapidity. In the present study [2], we first investigate the effect of hadronic dissipation on elliptic flow in a more quantitative way that a hydrodynamic description of the QGP is followed by a kinetic approach of the hadron phase. We next study the dependence of initial conditions on the elliptic flow. We find that a novel hydrodynamic initial condition based on the color glass condensate, whose cases are growing in d+Au collisions at RHIC together with deep inelastic scattering at HERA, gives a larger eccentricity and in turn leads to a larger momentum anisotropy than the conventional initial condition from Glauber model does. Therefore, whether the perfect fluid QGP is discovered depends strongly on the modeling of initial states in relativistic heavy ion collisions. Futhermore, we show various important observables such as an excitation function of integrated elliptic flow up to the LHC energy and pT dependences of elliptic flow for identified hadrons including  mesons. References: [1] T. Hirano and M. Gyulassy, Nucl. Phys. A 769 (2006) 71. [2] T. Hirano et al., Phys. Lett. B 636 (2006) 299. 14. ON THE NECESSITY TO INCLUDE EVENT-BY-EVENT FLUCTUATIONS IN EXPERIMENTAL EVALUATION OF ELLIPTICAL FLOW R.Andrade a, F.Grassi a, Y.Hama a, T.Kodama b, O.Socolowski Jr. c a Instituto de Física, USP, C. P. 66318, 05315-970 SaoPaulo-SP, Brazil, [email protected],[email protected],[email protected] b Instituto de Física, UFRJ, C. P. 68528, 21945-970 Rio de Janeiro-RJ , Brazil [email protected] c CTA/ITA, Pra\c{c}a Marechal Eduardo Gomes 50, Instituto de Física, UFRJ, 12228-900 SaoJosé dos Campos-SP, Brazil, [email protected] Elliptic flow at RHIC is computed event-by-event with NeXSPheRIO. We show that when symmetry of the particle distribution in relation to the reaction plane is assumed, as usually done in the experimental extraction of elliptic flow, there is a disagreement between the true and reconstructed elliptic flows (15-30% for  =0, 30% for p  =0.5 GeV). We suggest a possible way to take into account the assymetry and get good agreement between these elliptic flows. 15. ON THE STRONGLY-INTERACTING LOW-VISCOSITY MATTER CREATED IN RELATIVISTIC NUCLEAR COLLISIONS L. P. Csernaia, J. I. Kapustab and L. D. McLerranc for Theoretical Physics, Department of Physics, University of Bergen Allegt. 55, 5007 Bergen, Norway, [email protected] bSchool of Physics and Astronomy, University of Minnesota Minneapolis, MN 55455, USA, [email protected] c Nuclear Theory Group and Riken Brookhaven Center, Brookhaven National Laboratory, Bldg. 510A, Upton, NY 11973, USA, [email protected] aSection Substantial collective flow is observed in collisions between large nuclei at RHIC (Relativistic Heavy Ion Collider) as evidenced by single-particle transverse momentum distributions and by azimuthal correlations among the produced particles. The data are well-reproduced by perfect fluid dynamics. A calculation of the dimensionless ratio of shear viscosity  to entropy density s by Kovtun, Son and Starinets within AdS/CFT yields  /s = 1/4  which has been conjectured to be a lower bound for any physical system. Motivated by these results, we show that the transition from hadrons to quarks and gluons has behavior similar to helium, nitrogen, and water at and near their phase transitions in the ratio  /s. We suggest that experimental measurements can pinpoint the location of this transition or rapid crossover inQCD. 14 16. Heat capacity and average transverse momentum relevant to QGP phase transition Xiao-Mei Li1, Shou-Yang Hu1, Shou-Ping Li1, Jing Feng1, Dai-Mei Zhou2, and Ben-Hao Sa1,2 China Institute of Atomic Energy, P. O. Box 275 (18), Beijing, 102413 China 2 Institute of Particle Physics, Huazhong Normal University, Wuhan, 430079 China 1 Heat capacity is a measure of the temperature (energy) fluctuation and its singularity behavior is relevant to the phase transition. Average transverse momentum is closely related to temperature and thus concerned to the phase transition either. A parton and hadron cascade model, PACIAE \cite{sa}, is applied to calculate the pion transverse momentum distribution in pure Hadronic Matter scenario ("HM") and the parton (pion's precursor) transverse momentum distribution in pure Quark Gluon Matter scenario ("QGM") for 0-5\% most central Au+Au collisions at s NN =10, 17.3, 19.6, 62.4, 130, 200, 1000, and 5500 GeV event-by-event. In addition, the pion transverse momentum distribution is calculated in a third scenario of partonic matter being hadronized and followed by hadronic rescattering ("HM v. QGM", here "v" means "via"). If the temperature is extracted by fitting the transverse momentum distribution to a exponential distribution event-by event the heat capacity of the pion (      ,  0 decay assumed) in "HM" and "HM v.QGM" and of the parton ( u  u  d  d ) in "QGM" can be calculated due to the assumption in statistical physics that the temperature fluctuation should be a Gaussian distribution. The preliminary results seams showing that there is peak structure appearing in cv ( s NN ) at around s NN =17.3 GeV in "QGM" simulations. Both the  T  ( s NN ) and the  pt  ( s NN ) are increase with increasing of s NN in "QGM", "HM v. QGM", and "HM" calculations and the magnitude of abscissa of those curves is also in order of "QGM">"HM v. QGM">"HM" showing a possibility to study QGP phase transition according to  T  ( s NN ) and  pt  ( s NN ) . [1] Ben-Hao Sa, Dai-Mei Zhou, and Zhi-Guang Tan, J. Phys. G, 32, 243 (2006); Dai-Mei Zhou, Xiao-Mei Li, Bao-Guo Dong, and Ben-Hao Sa, Phys. Lett. B638(2006)461. 17. Understanding the initial state eccentricity in AA collisions a D. J. Hofmana for the PHOBOS collaboration Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA, [email protected] One of the early, important discoveries at RHIC was that the strength of the elliptic flow component, v2 , was not only large, but also for the first time reached the limit predicted by hydrodynamical calculations. In a hydrodynamics picture, elliptic flow is understood to be a consequence of the spatial anisotropy of the initial matter distribution. This anisotropy is usually characterized by the eccentricity of the overlap region of the colliding nuclei. Understanding and correctly calculating this initial state eccentricity is, therefore, also important in our studies of this interesting bulk property of the produced hot QCD matter, especially in the context of comparisons between different heavy-ion colliding systems, as first studies by PHOBOS have shown [1]. This talk will discuss various approaches to calculating the relevant initial state eccentricity, and its influence on the interpretation of the data in Cu+Cu and Au+Au collisions at RHIC. In particular, we will focus on the insight that can be gained from utilizing a Glauber Monte Carlo model of the initial state, coupled with an event-by-event eccentricity calculation relative to the principal axes of the participant distribution. We will also show systematic effects on the calculated eccentricity of performing the integrals over the binary collisions, as well as various data-motivated weightings. Possible effects that arise from moving beyond the standard point-like nucleon distributions to nuclei with smooth matter distributions will also be discussed. This latter approach may allow one to connect the role of eccentricity to the basic assumptions of hydrodynamics. References [1] S. Manly et al. (PHOBOS), Quark Matter 2005 Proceedings (in press);arXiv:nucl-ex/0510031. 15 This work was partially supported by U.S. DOE grants DE-AC02-98CH10886, DE-FG02-93ER40802, DE-FC02-94ER40818, MIT DE-FG02-94ER40865, DE-FG02-99ER41099, and W-31-109-ENG-38, by U.S. NSF grants 9603486, % Phobos TOF 0072204, Rochester until 6/03 and 0245011, Rochester starting 6/03 by Polish KBN grant 1-P03B-062-27(2004-2007), by NSC of Taiwan Contract NSC 89-2112-M-008-024, and by Hungarian OTKA grant (F 049823). 18. Jet Tomographic Tests of the CGC Initial State at RHIC and LHC A. Adila , and M. Gyulassya Columbia University, Department of Physics, 538 West 120th street New York, NY 10027. USA, [email protected] a Current claims for the perfectly fluid nature of the strongly interacting QCD matter (sQGP) at RHIC are based on the success of non-viscous hydrodynamics in describing bulk low p  collective observables [1]. These analyses, however, depend on the assumed initial state for  hydrodynamic evolution being determined by the local participant density ( Part ( x ; b) ). Using initial states corresponding to Color Glass Condensate (CGC) conditions in conjunction with non viscous hydrodynamics leads to a disagreement with data [2]. One thus needs an independent test of the initial state before any statements can be made about the applicability of non viscous hydrodynamics at RHIC and the resultant perfect fluidity. We propose detailed jet tomography via the nuclear modification factor RAA ( p ,  , y; b) as just such a test. CGC models generically lead to a higher spatial eccentricity in the transverse plane at mid rapidity than participant bulk models which can be probed by high p  jets via jet quenching leading to an enhanced second fourier moment v2 ( p ; b) of RAA ( p , ,0; b) . Furthermore, for y  0 both CGC and participant bulk models predict a twist' in the medium, shifting it off the origin in the transverse plane, leading to a non zero first fourier moment v1 ( p , y; b) . We present calculations of these observations for RHIC and LHC and discuss their usefulness when it comes to differentiating initial states as well as their sensitivity to model details (e.g. nuclear edge effects). This presentation is based on work done in [3]. References [1] T. Hirano, Acta. Phys. Polon., B36, p. 187-194, (2005) and references therein. [2] T. Hirano, U. W. Heinz, D. Kharzeev, R. Lacey, and Y. Nara, Phys. Lett. B636, p. 299-304, (2006). [3] A. Adil, and M. Gyulassy, Phys. Rev. C72, 034907 (2005). A. Adil, M. Gyulassy, and T. Hirano, Phys. Rev. D73, 074006 (2006). A. Adil, H-J. Drescher, A. Dumitru, A. Hayashigaki, and Y. Nara, arXiv:nucl-th/0605012. A. Adil, M. Gyulassy, W. Horowitz and S. Wicks, in preparation. 19. Identify Bottom Contribution in Non-photonic Electron Spectra and v2 from Au+Au Collisions at RHIC S. Esumia H. Huangb, Y. Miakea, S. Sakaia, N. Xuc, and Y. Zhangc of Physics, University of Tsukuba, Japan bDepartment of Physics and Astronomy, University of California, Los Angeles, USA cNuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, USA aDepartment In Au+Au collisions at RHIC, in the measured non-photonic electron spectra and v2 distributions both contributions from charm-hadrons and bottom-hadrons are mixed together. There are large uncertainties in the model predictions for charm and bottom production in high-energy nuclear collisions. In order to understand the hot/dense properties at RHIC, it is necessary to separate the charm from bottom contributions. However, the isolation of charm and bottom contributions remains a challenge. Due to the extremely heavy mass of the bottom quark, the effect of the interactions with medium is expected to be small. In addition, assuming the same D-meson over B-meso raitos in p+p and Au+Au collisions at RHIC, we make a simultaneous fit to both non-photonic electron R AA and v2 distributions. We found that the contribution of bottom is negligible for p  (electron) ≤5 GeV/c. This electron momentum is corresponding to both 16 D-meson and B-meson's p  up to 5-7 GeV/c. This result will provide useful/necessary constrain for heavy quark production model calculations. 20. Rapidity Dependency of Coalescence in Au+Au Collisions at s NN =200 GeV. C. Nygaarda, for the BRAHMS Collaboration a Niels Bohr Institute, The University of Copenhagen Blegdamsvej 17, 2100 Copenhagen, Denmark - [email protected] The BRAHMS Experiment at the RHIC measures charged particles at a wide range of deuteron rapidities, y ～0-3, offering a unique possibility to study the rapidity dependency of various physical phenomena. In this talk particle coalescence is used to study the rapidity dependency of the source size. As the collision fireball cools down and hadronizes it becomes possible for protons d 3Nd Ed dp d3 and neutrons to coalesce into deuterons. The coalescence parameter, B2  can be d 3N p 2 (E p ) dp 3p measured and theoretically connected to the volume of the fireball by thermodynamical and/or quantum mechanical models. Thus measurements of B2 can yield information about the density profile of the fireball at the time of hadronic freeze-out. This talk discusses the rapidity dependency of the B2 in s NN =200GeV Au+Au central (0-10%) collisions and for reference s NN =200GeV p+p collisions. The measurements of B2 are then used to estimate the rapidity dependent shape of the fireball as well as the average energy density of the fireball. 21. TWO-CHARGED-PARTICLE AZIMUTHAL ANGLE CORRELATION AS ANOTHER PRESENTATION OF ANISOTROPIC ELLIPTIC FLOW IN RELATIVISTIC HEAVY ION COLLISIONS Wu Yuanfang and Huang Yanping of Physics, Huazhong Normal University,Wuhan, Hubei, 430079, P.R.China, [email protected] aInstitute Two-charged-particle azimuthal angle correlation has been directly used in studying the anisotropy and correlation in transverse expansion of relativistic heavy ion collisions. It is demonstrated by the relativistic quantum molecular dynamics model (RQMD) and multiphase transport model (APMT) that two-charged-particle azimuthal angle correlation can serve as another good presentation for anisotropic elliptic flow, where the contributions from non-flow effects, such as momentum conservation are clearly indicated in the measure and resonance decay can be simply estimated from same and different sign two-charged-particle correlations. This measure has also been compared with currently suggested balance function in azimuthal angle. It makes the behavior of balance function in azimuthal angle more understandable. 22. ANISOTROPIC FLOW AT RHIC: HOW UNIQUE IS THE NUMBER-OF-CONSTITUENT-QUARK SCALLING ? Y. Lu¤ and F. Liu of Physics, Central China Normal University Wuhan, Hubei, 430079, P. R. China, [email protected] aInstitute The transverse momentum dependence of the anisotropic flow v2 for pion, kaon, nucleon, 17 Lambda, Xi and Omega is studied for Au+Au collisions at s NN = 200 GeV within string-hadron transport approaches UrQMD and RQMD. Although both models reach only 60\% of the absolute magnitude of the measured v2, it predicts the particle type dependence of v2, as observed by the RHIC experiments: v2 exhibits a hadron-mass hierarchy in the low pT region and a number-of-constituent-quark (ncq) dependence in the intermediate pT region. The failure of the hadronic models to reproduce the absolute magnitude of the observed v2 indicates that transport calculations of heavy ion collisions at RHIC must incorporate interactions among quarks and gluons in the early, hot and dense phase. The presence of the ncq scaling in the string-hadron model results suggests that hadronic interactions will also contribute to the observed particle-type dependence and the quark recombination may not uniquely explain the ncq scaling~[1]. ¤ in cooperation with: M. Bleicher, P. Sorensen, H. Stocker, N. Xu, X. L. Zhu References [1] Y. Lu, et al. J. of Physics G, 32, 1121, (2006). 23. Nuclear Stopping: Paving the way from RHIC to LHC H. H. Dalsgaarda for the BRAHMS collaboration Bohr Institute, The University of Copenhagen Blegdamsvej 17, Copenhagen 2100, Denmark, [email protected] aNiels Using data taken with the BRAHMS experiment at RHIC the rapidity and energy loss in Au+Au collisions at s NN =62.4GeV has been measured. For the first time at RHIC energies it is possible to resolve almost the entire baryon rapidity density, dN B  B ( y ) dy .The results show that the trend of the rapidity loss as a function of ybeam, defined as [1]: 2 ybeam dN B  B ( y ) y  ybeam  y dy N part 0 dy 1 saturates already around ybeam～4. An extrapolation is done using AGS, SPS and RHIC data [2] to estimate the rapidity loss at the LHC (ybeam～8.5$). The systematics of the baryon rapidity densities
up to the ybeam of RHIC will be used in the talk to predict the baryon rapidity density at the LHC.
Finally this is used to give a prediction for the charged particle multiplicity within the rapidity
coverage of the LHC.
References
[1] F. Videbaek, O. Hansen, Phys Rev Letters, C52 , 2684, 1995.
[2] BRAHMS Collaboration, I.G. Bearden et al, Phys Rev Letters, 93, 102301, 2004.
24.
Hadron pT spectra and blast-wave description of In-In collisions at the CERN SPS.
M. Florisa for the NA60 Collaboration
Dipartimento di Fisica, Universita degli Studi di Cagliari
Cittadella Universitaria, Monserrato (Cagliari), I-09042, Italy, [email protected]
a
NA60 is the only experiment that collected data in In-In collisions at 158~GeV/c at the CERN
SPS. The experiment was designed to measure dimuon production with high accuracy,
complementing a standard fixed target muon spectrometer with a silicon pixel vertex spectrometer.
The latter also measures all other charged particles produced in the interaction. So far no
measurement of freeze-out parameters for the indium system existed and the evolution models used
for In-In had to rely on extrapolation from Pb-Pb, with large associated uncertainties. In this talk we
will present the pT distributions of charged hadrons, measured in the target region with the vertex
spectrometer, and of the identified phi and omega mesons, measured via their decay to muon pairs.
These spectra are analyzed in the framework of a blast wave model to extract fireball parameters.
Comparison of our results to other SPS measurements provides new information and valuable
18
inputs for the description of the system-size dependence of the collision dynamics.
25.
Simulations of Elliptic Flow in Heavy-Ion Collisions with the CMS Experiment at the LHC
David Krofcheck for the CMS Collaboration
University of Auckland, New Zealand, E-mail [email protected]
The use of both silicon pixel and strip detectors in the CMS experiment at the LHC offers a
good probability of identification of very low pT charged particles. In this "soft" region of
pT  600MeV/c the elliptic flow coefficient v2 may be extracted from measured particle
correlations. The HYDJET Monte-Carlo event generator is used in this work to simulate elliptic
flow for Pb+Pb collisions at s NN = 5.5TeV. Second- and fourth-order cumulants are calculated
using pions, protons, and kaons for both central and semi-central collisions. The elliptic flow is
studied as a function of transverse momentum and pseudorapidity.
26.
Low pT Hadronic Physics with the CMS Detector at the LHC
F. Siklér for the CMS Collaboration
KFKI Research Institute for Particle and Nuclear Physics
H-1525 Budapest, P.O.Box 49, Hungary, E-mail [email protected]
The CMS experiment at the LHC will be equipped with 3 layers of silicon pixel and 11 layers
of silicon strip detectors embedded in a 4 T magnetic field within | |<2.5. The use of pixels alone
allows to employ similar reconstruction and analysis tools for low multiplicity p+p, p+A and high
multiplicity A+A events.
We will show first that three pixel barrels and four forward pixel disks (two in each z
direction) make the tracking of very low pT charged particles possible down to about 200MeV/c,
with good relative resolution. This can be achieved with good efficiency and negligible fake rate for
elementary p+p and p+A collisions, thanks to the information present in the shape of the pixel hit.
In case of central A+A the fake rate can be kept low for pT >400MeV/c.
Secondly, we will present the neutral and charged hadron identification capabilities of CMS at
low pT . A sizeable fraction of V 0 decays ( K s0      and   p  ) can be measured by
combining pairs of reconstructed charged tracks. Low pT photons are also measurable by
reconstructing conversions in the beam pipe and in the first pixel barrel layer. The use of the ADC
information (deposited energy) in pixels enables the identification of charged hadrons (   , K  ,p, p )
below 600~MeV/$c$ total momentum. A maximum likelihood method gives 9-10% relative dE/dx
resolution for minimum ionizing pions. In the region up to the crossing of the corresponding
Bethe-Bloch curves the inclusive yield of pions, kaons and protons can be extracted.
In summary the CMS experiment and its heavy-ion physics program is able to provide good
quality data for yields and spectra of identified charged and neutral particles, thus contributing to
the soft hadronic physics program of the LHC experiments.
27.
ENERGY CONSERVATION IN RELATIVISTIC HEAVY-ION COLLISIONS}
B. B. Back
Physics Division, Argonne National Laboratory, Argonne, IL 60439, U.S.A., [email protected]
Much attention has been devoted to the study of particle emission in the mid-rapidity region in
ultra-relativistic heavy-ion collisions because these particles are expected to carry information on
the conditions in the highest energy density regions of the hot and dense medium created in such
reactions. The present work [1] demonstrates, however, that essentially complete pseudorapidity
distributions of charged particles, without particle identification and momentum measurement, such
as those available from the PHOBOS experiment [2](Fig. 1a), allows for a reliable estimate of the
19
average transverse momenta and energy of emitted particles by requiring energy conservation in the
process. This analysis relies on the fact that most of the energy carried by the collision participants
appears at large pseudorapidities as shown in Fig. 1b. The results of such an analysis for Au+Au
collisions at s NN = 130 and 200 GeV are compared with measurements of mean- pT and
mean- ET in regions where such measurements are available as well as with predictions of
theoretical models. In addition, it is expected that the resulting energy density as a function of
pseudorapidity may be useful for setting initial conditions for hydrodynamic model calculations.
Figure 1: Panel (a): Pseudorapidity
distribution for 0-6% central Au+Au
collisions at 200 GeV [2] (solid points
and error band). Panel
(b): dE/d is plotted for a Gaussian 
dependence of < pT >i, shown in panel (c),
which is consistent with energy
conservation in the process. The estimates
of the  -distribution of net protons [3]
and their energy is shown as grey shading
in panels (a) and (b), respectively.
References
[1] B.B.Back, Phys. Rev. C72, 064906 (2005)
[2] B.B.Back et al. (PHOBOS), Phys. Rev. Lett. 91, 052303 (2003)
[3] I.G.Bearden et al. (BRAHMS), Phys. Rev. Lett. 93, 102301 (2004)
This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under
contract No. W-31-109-ENG-38.
28.
Anti-particle to particle ratios
in p+p, d+Au, Cu+Cu and Au+Au collisions at RHIC
Gábor I. Veresa for the PHOBOS Collaboration
Eötvös Loránd University, Budapest and MIT, Cambridge
ELTE TTK Dept. of Atomic Physics, H-1117 Budapest, Pázmány Péter sétány 1/A.
[email protected]
a
New results on anti-particle to particle ratios will be presented in Cu+Cu collisions at 62.4 and
200 GeV/nucleon energies, as a function of centrality and transverse momentum. The ratios are
measured close to midrapidity (0.1<  <1.4), in the 0.1 to 2.5 GeV/c transverse momentum range,
where most of the final state particles are found. Systematic features of these ratios as a function of
system size will be discussed for Au+Au, Cu+Cu, d+Au and p+p data. We observe that with
increasing system size from p+p to Au+Au, the antiproton to proton ratios significantly decrease,
carrying information about the balance between pair production and baryon transport.
The analysis techniques to determine anti-particle to particle ratios for identified protons, kaons
and pions will also be presented. In PHOBOS, particle identification is achieved by energy loss
measurements in the two-arm magnetic spectrometer, and by flight time measurements in the Time
of Flight walls. Experimentally, the precision of the measurement of anti-particle to particle ratios is
20
much increased by the fact that most of the corrections necessary to evaluate particle yields drop out
of their ratios.
Anti-particle to particle ratios in heavy-ion collisions are important probes in the systematic
study of the chemical freeze-out of the colliding system. Interestingly, no strong dependence of the
anti-particle to particle ratios on collision centrality or transverse momentum is found in heavy ion
collisions, in spite of the different nature of the possible production mechanisms for particles and
anti-particles.
This work was partially supported by U.S. DOE grants DE-AC02-98CH10886, DE-FG02-93ER40802,
DE-FC02-94ER40818, DE-FG02-94ER40865, DE-FG02-99ER41099, and W-31-109-ENG-38, by U.S. NSF
grants 9603486, 0072204, and 0245011, by Polish KBN grant 1-P03B-062-27(2004-2007), by NSC of Taiwan
Contract NSC 89-2112-M-008-024, and by Hungarian OTKA grant (F 049823).
29.
Multiparticle production to next-to-leading order in AA collisions
Raju Venugopalana and Francois Gelisb
of Physics, Brookhaven National Laboratory
Upton, NY, USA 11901, [email protected]
bService de Physique Th´eorique, Bˆat. 774, CEA/DSM/Saclay
, 91191, Gif-sur-Yvette Cedex, France, [email protected]
An outstanding problem in heavy ion physics is to compute multi-particle production from first
principles immediately after the collision. The initial inclusive multiplicity was computed in the
Color Glass Condensate framework to leading order in  S (but to all orders in the ratio QS2 / k 2 ,
where Q S2 is the nuclear saturation scale). It predicted values compatible with RHIC data on
multiplicities[1]. However to understand problems such as energy loss and thermalization from first
principles, one needs to do a consistent next-to-leading order computation (NLO in  S , but again,
to all orders in the above mentioned ratio). One ramification of great interest would be a consistent
treatment of both collisional and radiative energy loss effects. We describe recent work in achieving
this goal. Remarkably, the full NLO computation can be formulated as an initial value problem
[2], which means it can be computed using well known numerical techniques. We relate our results
to a recent 3+1-D Yang-Mills numerical computation of the Weibel instability in matter exploding
into the vacuum after a heavy ion collision [3]. The formulation of a kinetic theory which
interpolates between the initial glasma stage of the collision and the thermalized quark gluon
plasma is also discussed [4].
References
[1] A. Krasnitz and R. Venugopalan, Phys. Rev. Lett. 86: 1717, (2001); T. Lappi, Phys. Rev. C67:054903 (2003).
[2] F. Gelis and R. Venugopalan, hep-ph/0601209, to appear in Nucl. Phys. A; hep-ph/0605246.
[3] P. Romatschke and R. Venugopalan, Phys. Rev. Lett. 96:062302 (2006); hep-ph/0605045, to appear in Phys.
Rev. D.
[4] F. Gelis, S. Jeon and R. Venugopalan, in preparation.
30.
Forward nuclear modification factor in Au-Au and Cu-Cu collisions at
s =62.4GeV
Truls Martin Larsena for the BRAHMS Collaboration
aThe Niels Bohr Institute, University of Copenhagen
Blegdamsvej 17, 2100 Copenhagen, Denmark [email protected]
The high pT particles (e.g. mesons with pT > 2GeV/c) from 200 GeV Au-Au collisions are
produced from initial hard scattered partons. The hard scattered partons probe the final stages of the
created medium before the parton fragments. Studying high pT particles can then give information
on the final state effects of the created medium. The nuclear modification factor, ratio of
nucleus-nucleus particle yields scaled by the number of binary collisions to p+p yields, shows
suppression of the high pT particles in central collisions but no dependence on pseudorapidity [1].
In addition, RCP , binary collision scaled ratio of central to peripheral spectra, at the same energy
21
does not depend on pseudorapidity. At midrapidity in 62.4 GeV Au-Au and Cu-Cu collisions, it has
been shown that central collisions show no suppression or enhancement of the high pT particles,
while semi central collisions show Cronin enhancement [2]. At this lower energy, high pT particle
production can be studied in the fragmentation region. This could reveal interesting physics for
models, such as the Color Glass Condensate and Recombination[3]. Collisions at 62.4 GeV can be
used to bridge the data from SPS to RHIC, and constrain models spanning this energy regime.
Hadron spectra were measured from the p+p collisions at s NN =62.4GeV in June 2006 from
midrapidity out to the fragmentation region, a unique feature of BRAHMS. These results extends
the baseline measurements for the exploration of medium effects in heavy ion collisions.
In the talk I will present nuclear modification factors at forward rapidity for Au-Au and Cu-Cu
collisions using recent p+p collisions as reference data. Dependence on the system size will be
investigated through a ratio of Au-Au and Cu-Cu yields scaled by the respective number of binary
collisions, R AuCu .The R AuCu and the high pT suppression's dependence on pseudorapidity will
be presented in this talk.
References
[1] I. Arsene et al, BRAHMS Collaboration, Phys. Rev. Lett. 91, 072305 (2003)
[2] B. Alver et al, PHOBOS Collaboration, Phys. Rev. Lett. 96, 212301 (2006)
[3] R. C. Hwa and C. B. Yang, http://arXiv.org/abs/nucl-th/0605037 (2006)
31.
PARTICLE EMISSION FROM COLLISION SPECTATORS
B. B. Backa for the PHOBOS Collaboration
Division, Argonne National Laboratory
Argonne, IL 60439, U.S.A., [email protected]
aPhysics
In nuclear collisions at relativistic energies it is customary to label individual nucleons as either
participants or spectators. The majority of particles are produced inparticipant collisions'' and they
are predominantly emitted into a limited range of pseudorapidity. The remaining spectator nucleons,
which do not interact directly, are expected to continue along the beam axis as highly excited
fragments of nuclear matter, the decay products of which may receive a sufficiently large transverse
momentum kick to be detectable at large pseudorapidities.
Figure 1: Energy loss spectrum for particles
emitted into the 5.0< |η| <5.4 range in 19.6 GeV
Au+Au collisions (solid points) is compared to
HIJING Monte Carlo simulations (open points).
The spectrum has been corrected for the length
of trajectories through the Si wafers, but
background hits have not been subtracted.
Peaks corresponding to both singly and doubly
charged particles are observed in the data.
In this talk, we present direct evidence for spectator emission into the PHOBOS acceptance [1]
at large pseudorapidity for 19.6 GeV Au+Au and 22.4 GeV Cu+Cu collisions, namely the
observation of α-particles (and heavier nuclei) and an increased overall charged particle multiplicity
observed only in this η-region. We also present a simple model of particle emission from spectator
22
fragments that supports this interpretation. The centrality, species and pseudorapidity dependence
of these spectator decay products will be presented and discussed.
References
[1] B. B. Back et al. (PHOBOS), Nucl. Phys. A499, 603 (2003)
This work was partially supported by U.S. DOE grants DE-AC02-98CH10886, DE-FG02-93ER40802,
DE-FC02-94ER40818, DE-FG02-94ER40865, DE-FG02-99ER41099, and W-31-109-ENG-38, by U.S. NSF
grants 9603486, 0072204, and 0245011, by Polish KBN grant 1-P03B-062-27(2004-2007), by NSC of Taiwan
Contract NSC 89-2112-M-008-024, and by Hungarian OTKA grant (F 049823).
32.
Source Imaging of pion emission sources in Pb+Pb collisions at SPS energies
R. Lacey for the NA49 collaboration
Department of Chemistry, SUNY Stony Brook
Stony Brook, New York, 11794, USA, [email protected]
A deconfined phase of nuclear matter is expected to be formed at the high energy densities
created in relativistic heavy ion collisions. It is widely believed that important signatures for the
formation of such a phase are reflected in the space-time extent and the shape of particle emission
source functions. Recently, 1-Dimensional source imaging techniques have revealed a non-trivial
long range structure in the two-pion emission source at RHIC energies. The origins of this structure
are still under investigation. The presence or absence of such a structure in the pion emission
sources in heavy ion collisions at intermediate SPS energies could yield important information
which could help resolve its origins.
The NA49 Collaboration at SPS has carried out Pb+Pb collisions over a wide range of
bombarding energies during the last several years. In this presentation, the detailed 3-Dimensional
emission source functions for pions produced in central Pb+Pb collisions over the incident energy
range 20 AGeV to 160 AGeV will be shown. The pion source functions will be discussed in the
context of Gaussian shape assumptions and possible role of resonance decays.
33.
Counting valence quarks at RHIC and LHC.
aINFN
A.D. Polosaa
Roma, Dip. Fisica, Universitµa La Sapienza', Roma, Italy [email protected]
We consider the Nuclear Modification Ratios in heavy ion collisions, RCP and R AA , in the
region of intermediate transverse momentum, and study the dependency upon the constituent quark
model, validated by experimental information from STAR and PHENIX, we show that a clear
distinction is predicted for the f0(980) between the assumptions of ss or diquark-antidiquark
content[1].
References
[1] L. Maiani, A. D. Polosa, V. Riquer and C. A. Salgado, arXiv:hep-ph/0606217.
34.
System size and energy dependence of charged-particle multiplicity
distributions in p+p, d+Au, Cu+Cu and Au+Au collisions at RHIC.
Aneta Iordanovaa for the PHOBOS Collaboration
of Physics, University of Illinois at Chicago
Chicago, IL, 60607, [email protected]
The PHOBOS experiment at RHIC has performed a comprehensive study of the
charged-particle multiplicity produced in nucleus-nucleus collisions. The observed scaling
features of our data allow us to disentangle the various contributions to the bulk particle production
from different stages of the collision process, pointing to the importance of the initial stage to the
overall particle production.
The large acceptance of the PHOBOS multiplicity detector, which covers ±5.4 units of
pseudorapidity, makes unique measurements of the charged-particle distributions possible. In this
23
talk, we will present an extensive systematic study of the multiparticle production of p+p, d+Au,
Cu+Cu and Au+Au collisions at all RHIC energies, ranging from 19.6 GeV (Au+Au) to 410 GeV
(p+p). The newly analyzed Cu+Cu system, now including the lowest energy data at 22.4~GeV,
provides a bridge between the d+Au and Au+Au systems, in terms of the initial collision geometry.
The connection from Au+Au to d+Au and p+p is further augmented by a new analysis which
extends the Au+Au data for all energies to even more peripheral events, covering almost the full
collision cross-section. With the overlap in the number of participants between different collision
systems now greatly increased, a better systematic comparison of all the data can be made.
Starting from the elementary p+p collision environment, we compare the particle production as
modified by the cold" nuclear environment in d+Au and the hot" nuclear matter produced in
Au+Au collisions. The extensive coverage of the PHOBOS detector makes possible a close
examination of longitudinal features of particle production as well as measurement of the total
number of charged particles produced in the collisions. The centrality dependence of the yields
(both total and at midrapidity) exhibit scaling behaviours that appear to persist from the most
central Au+Au to peripheral Cu+Cu collisions.
This work was partially supported by U.S. DOE grants DE-AC02-98CH10886, DE-FG02-93ER40802,
DE-FC02-94ER40818, DE-FG02-94ER40865, DE-FG02-99ER41099, and W-31-109-ENG-38, by U.S. NSF
grants 9603486, 0072204, and 0245011, by Polish KBN grant 1-P03B-062-27(2004-2007), by NSC of Taiwan
Contract NSC 89-2112-M-008-024, and by Hungarian OTKA grant (F 049823).
35.
Source chaoticity in relativistic heavy collisions at SPS and RHIC
K. Moritaa and S. Muroyab and H. Nakamuraa
of Physics, Waseda University,Tokyo, 169-8555, Japan,
[email protected] (K. Morita), [email protected](H. Nakamura)
b
Matsumoto University, Matsumoto, 390-1295, Japan, [email protected]
We investigate two- and three-particle intensity correlation functions of pions in relativistic
heavy ion collisions for different colliding energies. Based on three models of particle production,
we analyze how chaotic the pion sources are in S+Pb and Pb+Pb collision at the SPS and Au+Au
collisions at the RHIC.
The chaoticity $\lambda$ of the two-particle correlation functions is corrected for long-lived
resonance decays by making use of a statistical model. The weight factor ω of the three-particle
correlator is extracted through a simultaneous χ2 fitting to both two- and three-particle correlation
function.
Using the 'true' (corrected for long-lived resonance decays) λ and the ω as inputs, we
alculate the chaotic fraction ε of the partially coherent source model, the mean number of coherent
sources α of the multicoherent source model and both of ε and α of the partially multicoherent
source model.
Although the partially coherent source model gives a result which is consistent with that of
STAR, the chaotic fraction does not show clear multiplicity dependence if we take into account
both of the corrected chaoticity and the weight factor of the three-pion correlation function. In the
analysis using the partially multicoherent model, we found that the upper bound of ε and the
lower bound of α were determined by the lower bound of ω if we take the partial Coulomb
correction of two-particle correlation function into account. From this fact, we also found that the
result of the partially multicoherent model indicated increasing number of coherent sources in
higher multiplicity events.
References
[1] K. Morita, S. Muroya, and H. Nakamura, Prog. Theor. Phys., v. 114, p. 583, 2005.
[2] K. Morita, S. Muroya, and H. Nakamura, Prog. Theor. Phys., in press, nucl-th/0602013.
36.
Centrality Dependence of Charged Hadron p_t Spectra at Forward Rapidities
in CuCu Collisions at s NN = 200
S. Bekele a
24
a
Department of Physics and Astronomy, The University ofKansas
Lawrence, KS, 66045, USA [email protected]
It has been found in AuAu collisions at RHIC that the total charged particle production scales
with the number of participants and the particle density in the mid-rapidity region changes
smoothly as a function of beam energy. The charged particle density reflects the time integral over a
variety of physics processes that play a role in particle production. Results from AuAu collisions at
s NN = 200GeV at RHIC show suppression of the high-p_t hadron yields at mid-rapidity in
contrast to the enhancement in high- p t hadron production observed in dAu collisions. Surprisingly,
comparable suppression has also been observed in both AuAu and dAu collisions at forward
rapidity. While the cause of the suppression at forward rapidity is not very well understood, the
suppression at mid-rapidity is believed to be due to final state effects such as partonic energy loss
in the dense medium. Comparing data from different collision systems may help us understand the
underlying mechanism for the suppression at forward rapidity. We present preliminary results from
the BRAHMS experiment on charged hadron p t spectra in CuCu collisions at s NN = 200 GeV.
The evolution of the particle density and nuclear modification factors is studied as a function of
centrality at forward rapidities. The results will be compared with observations from dAu and AuAu
collisions at the same energy. Scaling properties of particle production with respect to number of
participants and binary collisions will also be discussed.
This work was supported in part by the Office of Nuclear Physics of the U.S. Department of Energy.
37.
GLOBAL POLARIZATION OF QGP IN
NON-CENTRAL AA COLLISIONS AT HIGH ENERGIES
Zuo-tang Liang
Department of Physics, Shandong University, Jinan, Shandong 250100, China
Due to the presence of a large orbital angular momentum of the parton system produced at the
early stage of non-central heavy-ion collisions, quarks and anti-quarks are shown recently [1] to be
polarized in the direction opposite to the reaction plan which is determined by the vector of
impact-parameter and the beam momentum. The global quark polarization via elastic scattering was
first calculated in an effective static potential model and the result is given by [1],

p
1
Pq  
2 E E  mq 
where E and p are the energy and momentum of the initial quark in the c.m. frame of the parton
scattering, μ is the Debye screening mass of the quark in medium, which specifies the average
interaction range. While a more accurate and realistic calculation using the hard-thermal-loop
proporgator is underway and the numerical results are coming out [3], some of the measurable
consequences have been discussed [1,2]. It has been shown that such global quark polarization
should have many observable consequences. Global hyperon polarization from the hadronization of
polarized quarks are predicted [1] independently of the hadronization scenarios. The global
polarization of quarks and anti-quarks leads also to spin alignment of vector mesons.[2] Dedicated
measurements at RHIC are underway and some of the preliminary results are obtained [4,5].
In this presentation, the basic idea and main results of global quark polarization given in Refs.[1]
and [3] will be presented. The direct consequences such as global hyperon polarization
and spin alignmemnt are summarized.
[1] Z.T. Liang and X.N.Wang, Phys. Rev. Lett. 94:102301,2005, hys.Rev.Lett.96:039901,2006
[2] Z.T. Liang and X.N. Wang, Phys. Lett. B629, 20 (2005).
[3] S.W. Chen, J.H. Gao et al., in preparation.
[4] Ilya V. Selyuzhenkov for the STAR Collaboration, proceedings QM2005, Rom. Rep.
Phys.58:049-054,2006; e-Print Archive: nucl-ex/0510069.
[5] J.H. Chen for the STAR Collaboratio, submission to QM2006.
38.
25
PION ELLIPTIC FLOWS AND HBT INTERFEROMETRY
IN A GRANULAR QUARK-GLUON PLASMA DROPLET MODEL
W.N. Zhanga;b, Y.Y. Renb, and C.Y. Wongc;d
Department of Physics, Dalian University of Technology
Dalian, Liaoning, 116024, P. R. China, [email protected]
b
Department of Physics, Harbin Institute of Technology
Harbin, Heilongjiang, 150006, P. R. China, [email protected]
c
Physics Division, Oak Ridge National Laboratory
Oak Ridge, Tennessee, 37831 USA [email protected]
dPhysics Department, University of Tennessee, Knoxville, TN, 37996 U.S.A. USA
a
In many simulations of high-energy heavy-ion collisions on
an event-by-event basis, the initial energy density distribution in
the transverse plane consists of highly fluctuating domains (Fig.
1a)[1]. Subsequent rapid longitudinal expansion will lead to
many longitudinal quark-gluon plasma tubes (Fig. 1b), each of
which tends to break up into many spherical droplets because of
sausage instabilities (Fig. 1c). The occurrence of granular
droplets in highly energetic heavy-ion central collisions may be
much more prevalent than previously thought [2]. Furthermore,
the analysis of the HBT radii in the granular droplet model can be
successful because the particle emission time scales with the
initial radius of the droplet. Particles will be emitted earlier in a
granular droplet and will lead to a smaller extracted HBT Rout radius [3]. We are therefore
motivated to investigate concurrently the data of (1) the elliptic flow v2 as a function of pT , and
(2) various HBT radii as a function of K T , for Au + Au collisions at s NN =200GeV at RHIC.
We find that the data of HBT radii and the elliptic flow can be described well by a granular source
model with an anisotropic collective flow. Direct confirmation of the granular droplet
configuration may need to await more experimental work on single-event HBT correlations, as
suggested previously [4]. For details, see hep-ph/0606113 [2] which has been accepted for
publication in Phys. Rev. C.
References:
[1] H. J. Drescher, F. M. Liu, S. Ostapchenko, T. Pierog, and K. Werner, Phys. Rev. C65 054902 (2002); O.
Socolowski Jr., F. Grassi, Y. Hama, and T. Kodama, Phys. Rev. Lett. 93 182301 (2004); Y. Hama, et al:,
hep-ph/0510096.
[2] W. N. Zhang, Y. Y. Ren, and C. Y. Wong, hep-ph/0606113, in press in Phys. Rev. C.
[3] W. N. Zhang, M. J. Efaaf, and C. Y. Wong, Phys. Rev., C70, 024903 (2004).
[4] C. Y. Wong and W. N. Zhang, Phys. Rev. C70, 064904 (2004); W. N. Zhang, S. X. Li,
C. Y. Wong, and M. J. Efaaf, Phys. Rev. C71, 064908 (2005).
39.
THE EFFECT OF THE SPECTATOR CHARGE
ON THE CHARGED PION SPECTRA
IN PERIPHERAL ULTRARELATIVISTIC HEAVY-ION COLLISIONS
A. Szczureka b and A. Rybickia
Institute of Nuclear Physics PL-31-342 Cracow, Poland, [email protected]
b University of Rzeszów PL-35-959 Rzeszów, Poland
a
We estimate a novel electromagnetic effect of the spectator charge in peripheral Pb-Pb
collisions on the   and   spectra as a function of the Feynman xF , transverse momentum
and impact parameter at the SPS energies. We find quite large effect. The effect depends on the
initial conditions providing information on time and space characteristics of the pion creation
process. A deep hole in the   /   ratio is predicted at xF ～0.15 -- 0.20 and small transverse
momenta for peripheral collisions, fairly independent of the beam energy. The modification of the
spectra in Feynman xF and transverse momentum of the pion is quantified. The effect predicted
26
leads to a rather sizeable nuclear modification factor for   and   separately. Even when
averaged over   and   there is a residual effect. Clearly the electromagnetic effect violates
the isospin symmetry. We quantify this effect in the function of the Feynman xF and transverse
momentum of the pion. The conditions for creating pionic atoms are discussed.
The presentation is based on our recent analysis [1].
References
[1] A. Rybicki and A. Szczurek, a paper in preparation for Phys. Rev. C.
40.
Rapidity and pt Dependence of Identified-Particle Elliptic Flow at RHIC
S.J. Sanders and E.B. Johnson for the BRAHMS Collaboration a
of Physics and Astronomy, The University of Kansas
Lawrence, Kansas, 66045, U.S.A., [email protected]
a Department
Large azimuthal anisotropies are observed in the particle production with respect to the reaction
plane for non-central heavy-ion collisions at RHIC. Elliptic flow is measured by the 2nd harmonic
(v2) coefficient of the Fourier expansion of the azimuthal distribution. The observed anisotropies
and the measured v2(pt) values suggest an almost perfect fluid state is created, consistent with
the production of a strongly-interacting quark-gluon plasma[1]. Most measurements of
identified-particle v2(pt) behavior at RHIC have been done near mid-rapidity, although a strong
pseudorapidity dependence is seen for the charged- hadron, pt-integrated v2 values[2]. Some
theoretical progress has been made in understanding the dependence of the azimuthal flow on the
longitudinal expansion of the system[3,4,5], but these studies have lacked good comparison data on
the rapidity dependent change in <pt> and v2(pt) for different particle types. This talk will present
new results of the BRAHMS experiment on  , K and p v2(pt) behavior at y ≈ 0, 1, and 3. The
associated spectra will also be presented to help disentangle the kinematical factors affecting the
integral v2 values. These results can be used to better define the longitudinal expansion of the
medium created through heavy-ion reactions at RHIC energies. This work was supported in part by
the Office of Nuclear Physics of the U.S. Department of Energy.
References:
[1] E. Shuryak, Prog. Part. Nucl. Phys. 53, 273 (2004).
[2] B. B. Back et al., PRL 94, 122303 (2005).
[3] Ulrich Heintz and Peter Kolb, J. Phys. G 30, S1229 (2004).
[4] M. Csanad, T. Csorgo, and B. Lorstad, Nucl. Phys. A742, 80(2004).
[5] T. Hirano and Yashushi Nara, J. Phys. G 31, S1(2005), and T. Hirano, private commu-nication.
41.
Why even a small viscosity matters at RHIC
Denes Molnar (Purdue University, U.S.A.)
The remarkable success of interpreting RHIC data based on ideal hydrodynamics lead to the
conjecture that the quark-gluon plasma may in fact be a "perfect fluid", i.e., that viscos (dissipative)
effects are small. Though general quantum-mechanical arguments suggest a finite, nonzero
viscosity, calculations for N=4 supersymmetric Yang-Mills theory indicate a very small "minimal
viscosity" lower bound for the viscosity to entropy density ratio,  / s  1 / 4 . A similarly low
bound could hold, in principle, for dense quark-gluon matter as well.
In heavy-ion collisions, however, the relevant quantity is not the viscosity itself but the product
of the viscosity and spatial and temporal gradients. Because gradients are large, even a small
viscosity can affect the evolution significantly. In this talk I show how basic observables are
affected by even the "minimal" viscosity at RHIC, based on covariant transport theory. The
advantage of this approach is that it naturally incorporates dissipative effects (such as viscosity),
while it also has a hydrodynamic limit. The transport results will also be contrasted to (causal)
viscos hydrodynamics, an approach applicable for small deviations from local equilibrium.
42.
27
System size and rapidity dependence of the nuclear modification factor
R. Karabowicz for the BRAHMS Collaboration
Division of Hot Matter Physics, M. Smoluchowski Institute of Physics
Jagiellonian University, Krakow, 30059, Poland, [email protected]
The weak dependence on rapidity of the nuclear modification factor in Au+Au collisions at the
top RHIC energy is still not well understood [1]. Large particle suppression at midrapidity is
explained by parton energy loss in multiple scatterings in the strongly interacting dense medium. It
is of great importance to identify the mechanisms responsible for the small value of RAA observed at
large rapidities. Flow analysis at BRAHMS shows similar values of ν2 in mid-rapidity and forward
rapidity regions [2]. This results suggest common mechanisms underlying the observed suppression
in the wide rapidity range, which leads to the conclusion that QGP extends up to |y| ≈ 3. Alternative
approaches focus on the growing role of the initial state effects such as existence of the Color Glass
In the talk I will present nuclear modifcation factors obtained for identified hadrons in the Au +
Au collisions at √sNN = 200 GeV at various centralities and rapidities. An attempt to understand
the high-pT suppression phenomena in terms of the energy density will be undertaken.The results
will be compared with preliminary BRAHMS data on nuclear modification factors in Cu + Cu
collisions.
References:
[1] D. Rohrich, QM05 proceedings.
[2] H. Ito for BRAHMS Collaboration, QM05 proceedings.
43.
Energy and Centrality Dependence of Directed and Elliptic Flow
in Cu+Cu and Au+Au Collisions at RHIC Energies
Rachid NOUICERa for the PHOBOS Collaboration
Department, Brookhaven National Laboratory
Upton, NY 11973-5000, U.S.A. [email protected]
aChemistry
This work presents data taken by the PHOBOS experiment at RHIC showing directed and
elliptic flow of charged hadrons in Cu+Cu and Au+Au collisions at √sNN = 19.6, 22.4, 62.4 and
200 GeV as a function of pseudorapidity, centrality and transverse momentum. The measurements
of elliptic flow in 22.4 GeV Cu+Cu collisions and directed flow from Cu+Cu collisions at all
energies will be presented for the first time. These results will allow us to study the extended
longitudinal scaling observed previously in the Au+Au system. This work completes our systematic
study of flow measurements, providing an extensive and precise set of experimental data for Cu+Cu
and Au+Au collisions at RHIC ranging over an order of magnitude in energy.
The characterization of the collective flow of produced particles has proven to be one of the
most fruitful probes of the dynamics of heavy ion collisions at RHIC. Flow is sensitive to the early
stages of the collision and thus provides unique insights into the properties of the hot, dense matter
that is produced, especially about the degree of thermalization and the QCD equation of state. The
strong pseudorapidity dependence of elliptic flow revealed by the broad coverage of the PHOBOS
detector makes these results particularly useful for constraining the full three-dimensional
hydrodynamic evolution of the system.
This work was partially supported by U.S. DOE grants DE-AC02-98CH10886, DE-FG02-93ER40802,
DE-FC02-94ER40818, DE-FG02-94ER40865, DE-FG02-99ER41099, and W-31-109-ENG-38, by U.S. NSF
grants 9603486, 0072204, and 0245011, by Polish KBN grant 1-P03B-062-27(2004-2007), by NSC of Taiwan
Contract NSC 89-2112-M-008-024, and by Hungarian OTKA grant (F 049823).
44.
Yields and elliptic flow of d( d ) and 3He( 3 He ) in Au+Au collisions at √sNN = 200 GeV
Haidong Liua,b,c for the STAR Collaboration
of Modern Physics, University of Science & Technology of China
Hefei, 230026, P. R. China, [email protected]
bNuclear Science Division, Lawrence Berkeley National Laboratory,Berkeley, California, 94720
28
c
Physics Department, Brookhaven National Laboratory, Upton, New York, 11973
In ultra-relativistic heavy ion collisions, light nucleus and antinucleus production and their
elliptic flow are sensitive to the freeze-out conditions, such as temperature, particle density,local
correlation volume and collective motion at the moment when the particles decouple from the
system. These local properties at the last stage of the collisions provide a baseline for the
understanding of the collision system evolution.
In this talk, we present the transverse momentum spectra for deuterons, antideuterons (0.2 <pT
< 4 GeV/c) and helium-3, antihelium-3 (2 < pT < 6 GeV/c) at midrapidity in Au+Au collisions at
√sNN = 200 GeV measured in the STAR experiment at RHIC. We also present the coalescence
parameters B2 and B3, the antiparticle to particle ratios and the related centrality and pT dependence.
We present the first elliptic flow measurement for helium-3 and antihelium-3 in intermediate pT
region (2 < pT < 6 GeV/c) and the deuteron and antideuteron v2 measurement at 0.2 < pT < 3 GeV/c.
The results are compared to the baryon and meson v2 and the coalescence models.
45.
INCIDENT-ENERGY AND SYSTEM-SIZE DEPENDENCE OF DIRECTED FLOW
aUniversity
G. Wanga (STAR Collaboration)
of California, Los Angeles, California 90095, USA [email protected]
Directed flow (v1) describes collective sideward motion of produced particles and nuclear
fragments and carries information on the very early stages of the collision. The shape of v1(y) in the
central rapidity region is of special interest because it might reveal a signature for either QGP or
strong space-momentum correlations. At RHIC energies, it is a challenge to measure v1 accurately
because of the small magnitude of the signal itself and because of systematic errors due to non-flow
correlations and flow fluctuations. In this talk, STAR preliminary results for charged-particle v1 in
Au+Au and Cu+Cu collisions at √sN N = 200 and 62 GeV will be presented, with the two
above-mentioned systematic effects minimized by determining the reaction plane from spectator
neutrons.
Full comparisons among Au+Au and Cu+Cu at the two beam energies as
functions of pseudo-rapidity, pt and centrality are presented, and scaling behaviors like
Limiting Fragmentation are tested. Data are also compared with available models. STAR
prelinimary results indicate that at 200 GeV v1 shows similiarities between Au+Au and Cu+Cu.
46.
The inclusive photon and charged particle v2 at √sN N =200GeV in Au+Au and Cu+Cu
collisions
aPhysics
Guoji Lina for the STAR Collaboration
Department, Yale University, New Haven, CT, 06520, USA, [email protected]
Elliptic flow (v2) provides a direct probe of the thermalization and strong interaction in the
early stage of the heavy ion collision. Measuring flow for different particle species in different
phase space regions would provide information about the reaction dynamics of the system. Further,
there have been suggestions to measure the elliptic flow of direct photons to validate the existence
of jet-plasma interactions. Observation of direct photons and their elliptic flow necessitates a
measurement of inclusive photon v2, combined with a removal of the signal from decay photons.
In this talk the STAR preliminary result of inclusive photon and charged particle v 2 as a
function of pT and η in Au+Au and Cu+Cu collisions at √sN N = 200GeV will be presented.
Photons are identified in STAR Barrel Electro-magnetic Calorimeter (BEMC) and preshower
Photon Multiplicity Detector (PMD). Measuring the particle distribution with respect to the event
plane determined in another η region minimizes the contribution of non-flow correlation to v2
values. Decay photon v2 will be simulated using the known v2 and spectrum of charged
hadrons. The comparison between the inclusive photon v2 and the decay photon v2 may
provide an indication of the behavior of the direct photon v2.
47.
29
PHENIX MEASUREMENTS OF REACTION PLANE DEPENDENCE OF HIGH PT
PHOTONS AND PIONS IN Au+Au COLLISIONS
V. S. Pantuev, for the PHENIX Collaboration
Department of Physics and Astronomy, The University at Stony Brook
Stony Brook, New York, 11794-3800, USA, [email protected]
The study of high pT particle production at RHIC is one of the major experimental toolsto
investigate high-density state formed in the relativistic heavy ion collisions. This processis often
called ’jet tomography’. The nuclear modification factor, RAA, which is used to quantify nuclear
suppression, was successfully described by a variety of models with very different initial
assumptions. Extraction of the jet energy loss information from inclusive RAA is complicated
because RAA is a convolution of medium density, collision geometry and energy loss of high pT
partons. Large azimuthal anisotropy, v2, in particle yields at pT above 5 GeV/c remains a puzzling
result as a significant flow contribution at such a high momentum is unlikely. On the other hand,
traditional parton energy loss models give systematically smaller value of v2.
In contrast to the inclusive RAA, measurement of RAA versus the reaction plane is a tool to
change geometry keeping the same density profile. Such measurement is more informative than v2,
the latter one is the amplitude of RAA variation versus the angle in the reaction plane. It is useful to
combine information extracted from hadron production with electromagnetic signals, like direct
photons. Hard photons from early stage of the collisions along with negligible photon interaction
probability imply that the direct photon v2 should be zero. However, direct photons can also be
created as final processes in medium with both positive and negative contributions to the photon v2.
Thus, the measurement of direct photon v2 may constrain different model predictions.
In this talk we present PHENIX results on π0 production with respect to the reaction
plane.Such results will put strong restrictions on the parton energy loss parameters. Measurements
of RAA in reaction plane and particle anisotropy in a wide range of pT
provide insights on the
transition from soft to hard regions. We will also present recent high statistics results on direct
photon v2 at high pT. Various energy loss models will be compared with the data.
48.
v2 & v4 centrality, pt and particle-type dependence in Au+Au collisions at RHIC
aNIKHEF,
Yuting Baia for the STAR Collaboration
Kruislaan 409, 1098 SJ Amsterdam, The Netherlands, [email protected]
Anisotropy parameters (v1, v2, v4) carry information about early interactions in high-energy
nuclear collisions. Recent theoretical work, however, indicates a number of difficulties in
interpretation of experimental data because of ambiguities between possible assumptions of
equilibrium, equations-of-state, and modeling of the final hadronic phase[1,2,3]. In this talk, we
present STAR measurements of v2 and v4 for charged particle and identified particles as a function
of transverse momentum, rapidity and centrality. With high statistics, the mass-ordering and
quark-number scaling will be tested in different centralities. v4/v22 ratios for charged particle and
identified particles will be studied in detail. Comparisons to hydrodynamic predictions and
coalescence models will be made. These systematic studies can help us understand the collective
motion of the system, the degree of thermalization of the system, and the relevant
degrees-of-freedom at the time that the momentum space anisotropy is established.
References:
[1] R.S.Bhalerao, J.-P. Blaizot, N. Borghini, J.-Y. Ollitrault, Phys.Lett.B , 627, 49-54, 2005.
[2] Y. Lu, M. Bleicher, F. Liu, Z. Liu, P. Sorensen, H. Stoecher, X. Nu, X. Zhu, nucl-th /0602009
[3] P. Huovinen, P.V. Ruuskanen, nucl-th /0605008
49.
High-pT Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX
M. Konnoa for the PHENIX Collaboration
School of Pure and Applied Sciences, University of Tsukuba Tsukuba, Ibaraki, 305-8571,
Japan, [email protected]
Identified hadron analyses in heavy ion collisions at RHIC show particle type dependences of
30
hadron yields, especially a baryon/meson difference at intermediate pT (2∼5GeV/c). In central
Au+Au collisions at sNN = 200 GeV, there is a significant suppression in meson yield compared
to expectations from scaled p+p results. In contrast, a large enhancement of baryons relative to
mesons is observed in this pT region. The pT region is considered to have both soft and hard hadron
production mechanisms. Here, soft part includes hydrody-namic flow, quark recombination, etc. and
hard part includes jet fragmentation, which is well described by pQCD calculation. We also observe
some indications of transition from soft to hard hadron production, for example, in particle ratios.
Therefore, a detailed study of identified hadron spectra and yields in intermediate and higher pT
region could be effective to understand multiple hadron production mechanisms as mentioned
above.
The pT reach of charged hadron identification has been extended by high statistics data and the
introduction of an aerogel Cherenkov detector. We can now study the identified hadron production
at higher pT (up to 5GeV/c for charged pions, and 7GeV/c for (anti)protons) .sing the PHENIX
detector. In addition to heavy ion data (Au+Au, Cu+Cu at sNN = 200GeV) obtained in the past
RHIC runs, we have high statistics 200 GeV p+p data. The p+p data provides baseline spectra to
heavy ion data, and it is important to quantify in-medium nuclear effects in heavy ion collisions at
RHIC.
We will present high-pT identified hadron pT spectra (π/K/p and their antiparticles), particle
ratios, nuclear modification factors and their scaling properties in Au+Au and Cu+Cu collisions
at sNN = 200 GeV.
50.
Spin alignment of vector mesons (k*0,φ) in Au+Au and p+p collisions at
sNN = 200 GeV
Jin Hui Chen (For STAR Collaboration)
Nuclear Physics Division, Shanghai Institute of Applied Physics, CAS Shanghai, 201800, P. R. China,
[email protected]
Spin alignment of vector mesons is a unique probe of particle production mechanism.
References[1,2,3] showed that deviation of spin density matrix ρ00 from 1/3 could shed light on
particle production from coalescence or fragmentation of polarized quarks. In non-central
collisions bulk partonic matter with large angular momentum can be produced and the angular
momentum may be coupled to the spin of the vector mesons. Measurements of k*0, φ spin
alignment allow us to understand particle production and spin-orbital coupling from bulk partonic
matter to individual particles at intermediate transverse momentum. We will report the STAR
measurement of k*0, φ spin alignment up to transverse momentum pT = 5 GeV/c at mid-rapidity in
Au+Au and p+p collisions at sNN = 200 GeV. The production mechanism of k*0 and φ will be
discussed.
References
[1] Z.T. Liang, X.N. Wang, Phys. Lett. B, 629 (2005) 20-26.
[2] Z.T. Liang, X.N. Wang, Phys. Rev. Lett., 94 (2005) 102301.
[3] S.A. Voloshin nuch-th/0410089.
51.
Excitation functions of baryon anomaly and freeze-out properties at RHIC-PHENIX
T. Chujoa for the PHENIX Collaboration
of Physics, University of Tsukuba Tsukuba, Ibaraki, 305-8571, Japan,
[email protected]
aInstitute
The baryon anomaly is one of the surprising discoveries at the Relativistic Heavy Ion
Collider (RHIC). It brought us new ideas of hadronization processes and in-medium effects at
the extreme condition, such as a quark recombination, a hydrodynamical collective flow with
jet quenching, and a baryon junction in central Au+Au collisions at sNN = 200 GeV. The
31
measurements of (anti)proton to pion ratios and the nuclear modification factors RAA for
identified hadrons, as a function of beam energies in different collision systems, provide an
important information to study the onset effect of baryon anomaly at RHIC and its evolution in
detail. In 2004 and 2005 RHIC runs, the PHENIX experiment has accumulated the first
intensive lower beam energy data sets in Au+Au 62.4GeV, and in Cu+Cu 22.5, 62.4GeV.
We present the preliminary results of pT spectra, dN/dy, particle ratios, and RAA for
± ±
π /K /p/ p in Cu+Cu at sNN = 22.5 and 62.4GeV, and in Au+Au at 62.4GeV, measured by the
high resolution Time-of-Flight detector in PHENIX. We also show the beam energy and system
size dependences of hadron kinetic and chemical freeze-out properties at RHIC by performing
the blast wave fit and statistical thermal model fit for all available identified spectra results in
PHENIX; i.e. p+p (200GeV), d+Au (200GeV), Cu+Cu (22.5, 62.4, 200GeV), and Au+Au (62.4,
200GeV). The excitation function of the collective radial flow, baryon chemical potential,
yields, particle ratios will be reviewed. We will also report the latest status of pT spectra
measurement in p+p at 62.4GeV, which was newly taken in 2006 RHIC run by PHENIX and
will gives an important reference spectra for RAA in both Au+Au and Cu+Cu at 62.4GeV with
less ambiguities.
52.
Energy and system size dependence of photon production at forward rapidities at RHIC
Monika Sharmaa for the STAR Collaboration
of Physics, Panjab University Chandigarh, India, [email protected]
In relativistic heavy ion collisions, global observables like particle multiplicity and their
spatial distribution provide information on particle production mechanisms and the evolu- tion of
the system formed in the collisions. Photon multiplicity measurements at forward rapidity have
been carried out using a Photon Multiplicity Detector (PMD) [1] in the STAR experiment. First
results from this detector have provided useful insight into the mechanism of particle production at
RHIC [2].
In the present talk we discuss the energy and system size dependence of pseudorapidity (η)
and multiplicity distributions of photons measured in the region 2.3≤η≤3.7 for Au+Au and Cu+Cu
collisions at sNN = 200 and 62.4GeV. The results on the system size and energy dependence of
longitudinal scaling for photons will be discussed. Comparison of pseudorapidity distributions to
various particle production models will be presented.
References
[1] M.M. Aggarwal et al., Nucl. Instrum. Meth. A 499, 751 (2003).
[2] J. Adams et al., (STAR collaboration), Phys. Rev. Lett. 95, 062301 (2005).
53.
PHENIX Studies of the Scaling Properties of Elliptic Flow at RHIC Energies
Arkadij Taranenkoa, for the PHENIX Collaboration
of Chemistry, SUNY Stony Brook Stony Brook, NY, 11794, U.S.A.,
[email protected]
Elliptic flow measurements provide a sensitive probe of the thermodynamic and transport
properties of the hot and dense medium created in ultra- relativistic heavy ion collisions. Recent
measurements at RHIC, have been found to be compatible with perfect fluid hydro- dynamics for
several particle species measured over a broad range of pTs and centralities. A detailed test of
several scaling predictions of perfect fluid hydrodynamics can provide important experimental
constraints for the decay dynamics of the hot and dense QCD matter produced in such collisions.
A comprehensive analysis of the scaling properties of the fine structure of elliptic flow (i.e its
detailed dependence on transverse momentum, particle type, centrality, system size, colliding energy,
etc.) measured by the PHENIX collaboration in Au+Au/Cu+Cu collisions at sNN = 62.4-200GeV
will be presented. The implications of these scalings as constraints for the equation of state and the
32
transport coefficients will also be discussed.
54
Global polarization of Lambda hyperons in Au+Au collisions at RHIC
I. Selyuzhenkova for the STAR Collaboration
Department of Physics and Astronomy, Wayne State University
Detroit, MI, 48201, USA, [email protected]
a
The system created in a non-central nucleus-nucleus collision possesses large angular orbital
momentum. Due to the spin-orbital coupling, particles produced in such a system could become
globally polarized along the direction of the initial system angular momentum. Such transformation
of the angular orbital momentum into the particle spin can happen at dif- ferent evolution stages of
the system created in nucleus-nucleus collisions. Measurements of various observable consequences
such as global spin alignment of vector mesons and global hyperon polarization could be used as an
effective tool to probe the different hadronization mechanisms.
In this talk, we present the results of the global polarization measurements in Au+Au collisions at √sNN =62 GeV and 200 GeV performed with the STAR detector at RHIC. The global
polarization of the system is examined by measuring the polarization of Λ hyperons with respect to
the system angular orbital momentum, perpendicular to the collision reaction plane.
55
Energy and system size dependence of elliptic flow and v2/ε scaling
Sergei A. Voloshina for the STAR Collaboration
of Physics and Astronomy, Wayne State University
Detroit, Michigan, 48201, U.S.A.; E-mail: [email protected]
Elliptic flow measurements at RHIC are considered to be major tools for establishing the
creation and thermalization of strongly interacting Quark Gluon Plasma at RHIC. The evolution of
elliptic flow with collision energy and system size provides important information on the nature of
the matter created in nuclear collisions at high energies. In this talk, STAR preliminary results on
charged-particle integral and differential elliptic flow in Au+Au and Cu+Cu collisions at √sNN =200
and 62 GeV will be presented. Flow fluctuations, their relation to fluctuations in the initial system
eccentricity, and v2/ε scaling (dependence of the elliptic flow on the initial system eccentricity and
particle rapidity density) will be discussed.
II. Jet Quenching and Medium Modification of Jet Particles
56
Large p/π ratios at RHIC and LHC
Rudolph C.Hwa
Institute of Theoretical Science and Department of Physics
University of Oregon, Eugene, OR 97403-5203, USA, [email protected]
It has been known for several years that in Au-Au collisions at RHIC the proton-to-pion ratio at
midrapidity is around 1 at pT~3GeV/c, a phenomenon that has been successfully explained in the
recombination/coalescence model. We now extend the consideration to two other regions and show
that the ratio is even larger for different reasons. One is in the forward region at large η, where we
expect hadrons to be produced with xF>1, which is possible only by recombination of partons from
different nucleons. Because it is hard to have antiquarks at medium x but much easier to have light
quarks there to form proton, the p/πratio can exceed 2 for pT>2GeV/c [1]. The other region is for
10<pT<20GeV/c at midrapidity at LHC where jets are so copiously produced that the recombination
of shower partons from adjacent jets can lead to higher yield for protons, since they require less
parton momenta than pions. We estimate that the p/πratio can exceed 5 [2].
Another striking characteristic of hadron production in those regions is that treated as trigger
33
particles those hadrons do not have associated particles that are distinguishable from the
background, but the reasons are different for the two cases. The former is because no jets are
involved, while the latter is because there are too many jets present.
References:
[1] R.C.Hwa and C.B.Yang, nucl-th/0605037 (revised version to be submitted).
[2] R.C.Hwa and C.B.Yang, Phys. Rev. Lett. (to be published).
57
Mach cones and dijets - angular correlations as a probe of early medium
evolution
T.Renk a,b, K.Eskola a,b and J.Ruppert c
Department of Physics, PO Box 35, University of, Jyvaskylä
b Helsinki Institute of Physics, PO Box 64, Helsinki, FIN-00014, Finland, [email protected]
cPhysics Department Duke University, PO Box 90305
Durham, NC, 207708, USA, [email protected]
a
Hard processes are a well calibrated probe to study heavy-ion collisions. However, the
information to be gained from the nuclear suppression factor RAA is limited, hene one has to study
more differential observables to get a diagnostic tool of the medium. In particular, the angular
correlations of hadrons associated with a triggered hard hadron show a rich pattern when going
from low pT to high pT.Of prime interest is the fate of the away side parton with a trajectory through
the medium of on average several fm. At low pT , the pattern of associate hadrons can be understood
in terms of Mach shocks excited by the energy lost from the away side parton. At high pT , fluid
dynamics is not applicable any more and the correlations become dominated by the punchtrough of
the away side parton with subsequent fragmentation.
We present an analysis of these phenomena within a systematic study of different dynamical
models of fireball evolution and a realistic Monte Carlo simulation of the experimental trigger
conditions. We find that the expansion dynamics of the medium is important in the understanding
of long in-medium parton paths. Provided that the medium is modeled in a realistic way, we
demonstrate that within a state-of-the-art radiative energy loss formalism the measured dijet yield
can be explained without additional free parameters. Using information from lattice QCD about the
EOS of hot QCD matter, we also demonstrate that the lower pT correlation pattern can be
understood in terms of Mach shocks induced by lost energy. We show that this scenario is also in
agreement with the measured 3-particle correlations. We explicitly show what information about
the medium can be derived from these observables.
References:
[1] T.Renk, hep-ph/0607166.
[2] T.Renk, hep-ph/0607035.
[3] T.Renk and J.~Ruppert, hep-ph/0605330.
[4] T.Renk, hep-ph/0602045.
[5] T.Renk and J.~Ruppert, Phys.\ Rev.\ C {\bf 73} (2006) 011901.
[6] T.Renk and J.~Ruppert, Phys.\ Rev.\ C {\bf 72} (2005) 044901.
58
DOES THE CRONIN PEAK DISAPPEAR?
G.G. Barnaf¨oldia,b, P. L´evaia, G. Pappb, G. Faic and B.A. Coled
aRMKI Research Institute for Particle and Nuclear Physics
P.O. Box 49, Budapest H-1525, Hungary, [email protected], [email protected]
bE¨otv¨os University, P.O. Box 32, Budapest, H-1518, Hungary, [email protected]
cCenter for Nuclear Research, Kent State University,Kent, OH 44242, USA, [email protected]
dNevis Laboratory, Columbia University,New York, NY 10027, USA, [email protected]
In this work we compare the nuclear modification factors in pA and (dAu at RHIC) collisions
at CERN SPS, FNAL and RHIC energies in a wide pT range. In these experiments the nuclear
modification factor has shown an enhancement at pT _ 4 GeV/c. It was found also, the height of
34
this ’Cronin peak’ depends on the c.m. energy of the collisions corresponding to the stronger
shadowing at higher energies [1,2,3]. The aim of this talk is to analyze the shadowing phenomena at
lower (2 GeV/c < pT < 4 GeV/c) and intermediate (4 GeV/c< pT < 8 GeV/c) transverse momentum.
Different shadowing parameterizations are considered and the obtained Cronin peaks are
investigated at RHIC and LHC energies [4]. The goal of this research is to understand if final state
effects, e.g ’cold quenching’ can play a role in the higher-pT hadron productions.
References
[1] Y. Zhang, G. Fai, G. Papp, G.G. Barnaf¨oldi and P. L´evai Phys.Rev. v. C65, p. 034903,2002.
[2] G. Papp, P. L´evai, G.G. Barnaf¨oldi, Y. Zhang and G. Fai, Acta Phys.Polon., v. B32, p. 4069-4078, 2001.
[3] G.G. Barnaf¨oldi, P. L´evai, G. Papp and G. Fai, Acta Phys. Hung., v. A22, p. 325-334,2005.
[4] G.G. Barnaf¨oldi, P. L´evai, G. Papp and G. Fai, Nucl.Phys. v. A749, p. 291-294, 2005.
59
ARE JETS QUENCHED IN COLD NUCLEI?
I.Vitev
Los Alamos National Laboratory, Theoretical and Physics Divisions, Mail Stop H846
Los Alamos, NM 87545 USA, [email protected]
We use formal recurrence relation approach to multiple scattering to find the complete solution
to the problem of medium-induced gluon emission from partons propagating in cold nuclear matter
[1]. The differential bremsstrahlung spectrum, which includes all Landau-Pomeranchuk-Migdal
destructive interference effects, is calculated for three different cases: (1) a generalization of the
incoherent Bertsch-Gunion solution for asymptotic on-shell jets, (2) initial state energy loss of
incoming jets that undergo hard scattering and (3) final state energy loss of jets that emerge out of a
hard scatter. Our analytic solutions are given as an infinite opacity series which represents cluster
expansion of the sequential multiple scattering. These new solutions allow, for the first time, direct
comparison between initial and final state energy loss in cold nuclei. Contrary to the naive
assumption, we demonstrate that energy loss in cold nuclear matter can be large. Numerical results
to first order in opacity show that, in the limit of large jet energies, initial and final state energy loss
exhibit different path length dependence, linear versus quadratic, in contrast to earlier findings. In
addition, in this asymptotic limit initial state energy loss is considerably larger than final state
energy loss. These new results have significant implications for heavy ion phenomenology in both
p+A and A+A reactions. We demonstrate that the quenching of jets in cold nuclei is a dominant
effect in the suppression of the forward rapidity particle production in p(d)+A collisions [2].
Comparison to neutral pion data from STAR and muon data, corresponding to charged hadron and
heavy meson measurements, from PHENIX in the forward direction will be shown in a perturbative
QCD model which includes dynamical calculations of high twist shadowing and initial state energy
loss.
References:
[1] I.Vitev, in preparation.
[2] I.Vitev, T.Goldman, M.B.Johnson and J.W.Qiu, hep-ph/0605200.
60
ENERGY LOSS OF HIGH ENERGY PARTONS IN HOT QGP AND HIGH PT
PHOTONS
S. Jeona,b, S. Turbidea, C. Galea and G. Moorea
[email protected]
bThe presenting author.
I will present our calculation of the nuclear modification factor of neutral pions and the photon
yield at high pT in central Au-Au collisions at RHIC (√s =200 GeV) and Pb-Pb collisions at the
LHC (√s =5500 GeV).Our treatment of jet energy loss includes all leading orderQCD effects in hot
QGP. Unlike conventional approaches, the medium is treated as a fully thermal medium instead of a
collection of static scatterers.
As such we are able to evolve a physical description of the initial spatial distribution of jets
through an expanding medium up to their fragmentation. We reproduce the nuclear modification
35
factor of pion RAA at RHIC, assuming an initial temperature Ti =370 MeV and a formation
time τi =0.26 fm/c, corresponding to dN/dy = 1260. The resulting suppression depends on the
particle rapidity density dN/dy but weakly on the initial temperature. Thejet energy loss treatment is
also included in the calculation of high pT photons. Photons coming from primordial hard N-N
scattering are the dominant contribution at RHIC for pT > 5 GeV, while at the LHC, the range 8 <
pT < 14 GeV is dominated by jet-photon conversion in the plasma.
References:
[1]S. Turbide, C. Gale, S. Jeon and G. D. Moore, Energy loss of leading hadrons and direct photon production in
evolving quark-gluon plasma, Phys. Rev. C 72, 014906 (2005)
[2]S. Jeon and G. D. Moore, Energy loss of leading partons in a thermal QCD medium,
Phys. Rev. C 71, 034901 (2005)
61
Calculation of Hard Probe - Medium Interactions in 3D-Hydrodynamics
Steffen A.Bassa
of Physics, Duke University, Durham, NC, 27708-0305, USA,[email protected]
A full understanding of ultra-relativistic heavy-ion reactions requires the calculation of the
dynamics of bulk QCD matter, of the hard probes and of the probe-medium interactions in one
single consistent framework. However, currently there exists a disconnect between the hard and soft
regimes: whereas the dynamics of bulk QCD matter is very well described by fully 3D
hydrodynamical and hybrid macro+micro transport models, most calculations involving hard
probes rely on simplified and schematic parametrizations of the medium. These simplified
parametrizations induce large systematic uncertainties which severely limit the analytic power of
these calculations.
In this paper, we utilize a state-of-the-art fully 3-dimensional hybrid hydro+micro transport
model [1] to describe the space-time evolution of bulk QCD matter. The model employs relativistic
3D-hydrodynamics for the early, dense, deconfined stage of the reaction and a microscopic
non-equilibrium model for the later hadronic stage where the equilibrium assumptions are not valid
anymore. It is capable of self-consistently calculating the freezeout of the hadronic system, while
accounting for the collective flow on the hadronization hypersurface generated by the QGP
expansion. The initial conditions of the hydrodynamic calculation are tuned to describe the hadronic
data in the soft sector, such as hadron yields, spectra, rapidity-distributions as well as radial and
elliptic flow.
Having determined the properties and dynamics of the soft sector, we can now utilize the
time-evolution of the medium provided by our model for the calculation of jet energy-loss [2,3],
di-hadron correlations [3], charm diffusion [4] and other probe-medium interaction phenomena in a
consistent fashion. Due to the medium having been determined by the data in the soft sector, our
calculation significantly reduces the systematic uncertainties usually associated with the medium
parametrization and allows for a precision calculation of the aforementioned effects. We will
present the results of our calculation and compare them to data.
References:
[1] C.Nonaka and S.A.Bass, arXiv:nucl-th/0607018.
[2] T.Renk and J.Ruppert, Phys.\ Rev.\ C {\bf 72}, 044901 (2005).
[3] A.Majumder, arXiv:nucl-th/0412061.
[4] S.A.Bass and M.Asakawa, manuscript in preparation
62
Quark and gluon jet conversions in the quark-gluon plasma
Wei Liua , C. M. Kob , and B. W. Zhangc
a Cyclotron Institute and Physics Department, Texas A&M University
College Station, Texas, 77843-3366, U.S.A., [email protected]
Quark and gluon jet conversion rates in the quark-gluon plasma through both the elastic
process q(q̄)g → gq(q̄) and theinelastic process qq̄ ↔ gg are studied in the lowest order in Quantum
36
Chromodynamics. Using the Fokker-Planck approach to treat the propagation and conversion of
quark and gluon jets in the expanding quark-gluon plasma produced in relativistic heavy ion
collisions,we have found a net conversion of quark jets to gluon jets. This reduces the difference
between the nuclear modification factors for quark and gluon jets in central heavy ion collisions and
+
thus enhances the p/π and p̄/π
−
ratios at high transverse momentum. To explain the observed
similarity between these ratios at high transverse momentum in central Au+Au collisions at
NN=
200GeV [1]and those in p+p and d+Au collisions at same energy [2] requires, however, a much
larger net quark to gluon jet conversion rate than the calculated one [3]. Implications of our results
are discussed.
References
[1] STAR Collaboration, J. Adams {\it et al.}, nucl-ex/0606003.
[2] STAR Collaboration, J. Adams {\it et al.}, Phys. Lett.B 637, 161 (2006).
[3] W. liu, C. M. Ko, and B. W. Zhang, nucl-th/0607047.
63
Parton Energy Loss at Twist-Six in Deeply Inelastic e-A Scattering
Yun Guo
Institute of Particle Physics, Huazhong Normal University, Wuhan, 430079, P. R. China,
[email protected]
Co-authors: Ben-Wei Zhang, Enke Wang
Jet quenching, or parton energy loss induced by multiple scattering in high-energy nuclear
collisions has been proposed as a very sensitive probe of the properties of the hot and dense
medium[1-3], which recently has given a compelling theoretical explanation for many exciting
experimental phenomena observed at RHIC. To investigate the radiative energy loss, twist
expansion approach has been developed to derive parton energy loss in terms of the modified parton
fragmentation functions in nuclei within the framework of generalized factorization theorem[4,5],
and provides the first evidence that the A2/3 dependence of the jet energy loss describes very well
the HERMES data in e-A deeply inelastic scattering (DIS)[3].
We extend the twist expansion approach to study the parton multiple scattering at higher
twist(twist-6) of DIS in nuclei[6].Within the framework of the generalized factorization in pQCD,
we investigate the multiple parton scattering and induced parton energy loss at twist-6 in deeply
inelastic e-A scattering with the helicity amplitude approximation. It is shown that the fractional
energy loss induced by gluon radiation at triple scattering (twist-6) has a biquadratic dependence of
the nuclear size RA. Compared to the contribution of double scattering, the energy loss from the
twist-6 expansion has a αsR2 /Q2 suppression (Q is the momentum transfer) due to LPM
interference effect. The expanding parameter of twist-expansion αsR2 /Q2 is discussed and we find
the resummation of all higher twist processes should be needed for intermediate Q2 and heavy
References
[1]X.-N. Wang and M. Gyulassy, \textit{Phys. Rev. Lett.} 68 (1992) 1480
[2] M. Gyulassy and M. Pl\"umer, \textit{Phys. Lett.} B 243 (1990) 432
[3]E. Wang and X.-N. Wang, \textit{Phys. Rev. Lett.} 89 (2002) 162301
[4] X.-F. Guo and X.-N. Wang, \textit{Phys. Rev. Lett.} 85 (2000) 3591
[5] X.-N. Wang and X.-F. Guo, \textit{Nucl. Phys.} A 696 (2001) 788
[6]Yun Guo, Ben-Wei Zhang and Enke Wang,arXiv:hep-ph0606312
64
Parton Thermalization and Energy
Loss in ultrarelativistic Heavy Ion Collisions within a Parton Cascade
Z. Xua, A. Ela, O. Fochlera, and C. Greinera
aInstitut fu¨r Theoretische Physik, 1 Max-von-Laue-Str.
Johann Wolfgang Goethe-Universita¨t Frankfurt, Frankfurt am Main, 60438, Germany
[email protected]
We investigate parton thermalization and energy loss of high pT jets in the course of
37
space-time evolution of partons, simulated in a 3+1 dimensional pQCD inspired on-shell parton
The contributions of elastic gg ↔ gg as well as inelasticgg ↔ ggg pQCD processes to kinetic
equilibrationare manifested by the transport collision rates and calculated by choosing different
initial conditions of partons produced in a central Au+Au collision at RHIC energy. We find that
pQCD Bremstrahlung processes are much more efficient for momentum isotropization compared to
elastic scatterings. For the parameters chosen the ratio of their transport collision rates amounts to
5:1. This value is much larger than that one may expect when comparing their transport cross
sections.
Also the way thermalization occurs is investigated and compared with the famous
Bottom-Up'' scenario [2]. It turns out that whether theBottom-Up'' scenario is justified depends
strongly on the initial conditions. The detailed balance of inelastic scatterings moderates the
suggested scenario.
We calculate the nuclear modification factor RAA for high pT partons by dividing the final to
the initial pT spectrum.The results imply a stronger energy loss compared with the experimental
data. A detailed study of the dependence of the pQCD Bremsstrahlung processes on the LPM
suppression is in progress.
References
[1] Z.Xu and C.Greiner, Phys.Rev.C 71, 064901, 2005.
[2] R.Baier, A.H.Mueller, D.Schiff and D.T.Son, Phys.Lett.B 502, 51-58, 2001.
65
Heavy
Flavor Physics at RHIC and
LHC
Magdalena Djordjevic
Department of Physics, The Ohio State University
Columbus, Ohio 43212, USA [email protected]
Heavy quark production and attenuation patterns will provide unique tomographic probes of
QCD matter created in Ultrarelativistic Heavy Ion Collisions. In this talk I will present the
collisional [1] and radiative [2,3] energy loss mechanisms that we developed. In addition, I will
present the heavy flavor and single electron suppression predictions relevant for RHIC and LHC,
which are obtained from our theory [4,5]. Our results show that the radiative energy loss alone is
not able to explain the data on single electron suppression in central Au+Au collisions at RHIC
[4]. However, we show that the inclusion of collisional energy loss significantly improves the
agreement between the theory and the data [5]. Finally, I will discuss the ongoing work on the
energy loss computations in dynamically expanding medium.
References:
[1] M. Djordjevic, nucl-th/0603066 (2006).
[2] M. Djordjevic and M. Gyulassy, Nucl. Phys. A 733, 265 (2004).
[3] M. Djordjevic, Phys. Rev. C 73, 044912 (2006).
[4] M. Djordjevic, M. Gyulassy, R. Vogt and S. Wicks, Phys. Lett. B 632, 81 (2006).
[5] S. Wicks, W. Horowitz, M. Djordjevic and M. Gyulassy, nucl-th/0512076 (2006).
66
Simulation of jet quenching observables in Heavy Ion Collisions at the LHC
Gabor Veres (for the CMS Collaboration)
University of Budapest, Budapest,Hungary, E-mail [email protected]
Measurements at the LHC will be the first ones where isolating and studying the properties of
fully formed high energy jets in heavy-ion collisions will be possible. To estimate the feasibility and
precision of jet energy and correlation measurements, a Monte-Carlo event generator is needed,
which models hard collisions and parton energy loss in a heavy-ion environment, as well as general
hydrodynamical features, multiplicity, azimuthal anisotropy, fluctuations of the underlying soft
heavy ion event.The HYDJET event generator[1] was used in these studies, which was adjusted to
reproduce the expected dN/dη and v2 distributions based on extrapolations from the RHIC data, and
to provide a centrality dependence of multiplicity similar to that observed at RHIC.
38
Various observables connected to jet quenching in heavy-ion collisions at the LHC were
simulated, and the feasibility to isolate these from the underlying heavy-ion event by making use of
the CMS calorimeter coverage and segmentation was investigated. The studies include jet
transverse energy spectra; fragmentation functions;correlations between the partners of a
dijet;nuclear modification factors at high pT and the benefits of high level triggering on the
statistical errors of these observables.
References
[1] A Model of jet quenching in ultrarelativistic heavy ion collisions and high-pT
Lokhtin and A.M. Snigirev, Eur.Phys.J. C 45, 2006
67
IDENTIFIED PARTICLE NUCLEAR MODIFICATION FACTORS
AT RAPIDITY 2 - 3.8 IN AU+AU COLLISIONS AT
=200 GEV
C. Risteaa, for the BRAHMS Collaboration
aThe Niels Bohr Institute, University of Copenhagen
Blegdamsvej 17, 2100 Copenhagen, Denmark, [email protected]
One of the most interesting phenomena observed at RHIC is the strong suppression of the high
pT hadrons measured in central Au+Au reactions, relative to p+p collisions or peripheral spectra
scaled by the number of binary collisions [1].
At forward rapidity, the relative contributions due to jet quenching,recombination or gluon
saturation are yet to be understood. The baryons do in contrast to the mesons not show suppression
in the intermediate pT range of 2-4 GeV/c. This is likely related to Cronin and parton recombination
effects [2]. In the forward region where the initial parton density is not so large, the exponential
shape of the spectra could be related to the particle production from thermal partons only.
Hydrodynamic calculations with initial gluon distribution from the Color Glass Condensate could
also reproduce the multiplicity distribution, centrality and rapidity dependence of the nuclear
modification factor in Au+Au collisions at
=200 GeV [3].
The BRAHMS experiment has carried out measurements over broad range in rapidity, both for
Au+Au and p+p collisions at 200 GeV. In this talk,we shall present pT spectra for different event
centralities (minimum bias spectra for p+p) in narrow rapidity ranges (± 0.1), for midrapidity and
off-midrapidity (up to 3.8), for charged hadrons as well as for identified particles. The BRAHMS
measurements at forward rapidities for charged hadrons are unique for the RHIC experiments.
Nuclear modification factor RAA for directly identified baryons and mesons, as well as for inclusive
charged hadrons, at rapidities from 0 to 3.8
will be shown and discussed.
References
[1] I.Arsene et.al, BRAHMS Collaboration, Nucl. Phys.A757, 1-27, 2005.
[2] R.Hwa and C.B.Yang, nucl-th/0512075.
[3] T.Hirano and Y.Nara, nucl-th/0404039.
68
SPATIO-TEMPORAL IMAGING OF THE QUARK GLUON PLASMA
VIA JET MODIFICATION
A. Majumder
Department of Physics, Duke University, Durham, NC, 27708, USA, [email protected]
Hard jets produced in a high energy heavy-ion collision pass through various amounts of dense
matter prior to escape and fragmentation into hadrons. In the well defined formalism of perturbative
QCD, in the collinear limit, such modifications arise as length enhanced higher twist corrections. A
comprehensive analysis of the large number of high pT observables requires realistic modelling of
the geometry and space-time evolution of the produced plasma. Comparisons with experimental
data on single inclusive observables allow for the extraction of the averaged forward-light-cone
gluon field strength hF +µ F + ias experienced by the jet. Given sufficient differential experimental
information (on both single inclusive and multiparticle correlations) it may even be possible to
39
recreate a visual space time picture of the gluon density profile. To this end, a variety of initial
conditions and space-time evolution criteria will be subjected to the existing high pT spectra and
correlation observables, in an effort to examine their sensitivity to the plasma profile and to weed
down the various possible scenarios for the space-time image of the quark gluon plasma. Such an
effort also holds promise for the construction of more effective observables capable of probing
deeper into the structure of the dense deconfined matter.
69
Enhancement studied with
neutral pions from p+C, p+Pb, and Pb+Pb Collisions at
=17.2 GeV
K. Reygersa for the WA98 Collaboration
a
University of Mu¨nster, Institut fu¨r Kernphysik, 48149 Mu¨nster, Germany,
[email protected]
A comprehensive understanding of jet-quenching in heavy-ion collisions requires the study of
its energy dependence. Jet-quenching models are able to describe the high- pT hadron suppression at
RHIC energies whereas the amount of jet-quenching at CERN SPS energies remains an open
question.The WA98 collaboration has published neutral-pion spectra for Pb+Pb collisions at
=17.2GeV [1]. However, in addition to the Pb+Pb measurement the study of a possible pion
suppression at the CERN SPS requires a reference spectrum measured at the same energy and a
good understanding of the nuclear kT effect (Cronin enhancement).Therefore, neutral-pion spectra
in p+C and p+Pb at
=17.2 collisions GeV will be presented in this talk. The neutral-pion
spectrum in p+C provides a useful reference for the Pb data measured in the same experiment. The
nuclear kT enhancement can be studied by comparing neutral-pion production in p+C and p+Pb. A
better understanding of the Cronin effect at CERN SPS energies not only is important for the study
of jet-quenching but also for the interpretation of the WA98 Pb+Pb direct-photon data [2].
Depending on the amount of nuclear kT enhancement models are able to describe the direct-photon
spectrum in central Pb+Pb collision with different initial temperatures of the fireball. Thus, a better
constraint of the nuclear kT effect will also result in tighter limits on the initial temperature.
References
[1] WA98 Collaboration, Eur.Phys.J.C 23, 225-236, 2002
[2] WA98 Collaboration, Phys.Rev.Lett. 85, 3595-3599, 2000
70
Study of Jets in Heavy Ion Collisions with the CMS detector at the LHC
C. Roland for the CMS Collaboration
Massachusetts Institute of Technology, Cambridge, MA 02139 USA
E-mail [email protected]
Large transverse momentum jets provide unique tools to study QCD and dense matter in
high-energy heavy-ion collisions. Recent results on the suppression of high transverse momentum
particles in Au+Au collisions at
= 200 GeV indicate a pronounced energy loss of leading
partons in the dense and strongly interacting matter formed in these collisions. Extension of the
heavy-ion research program to LHC energies of
= 5.5 TeV will, for the first time, allow
the study of these effects directly through the fully reconstructed, highly energetic jets.The CMS
Heavy-Ion group has performed extensive studies on the possibility of measuring jet properties in
heavy-ion collisions. The CMS detector combines large acceptance calorimetry augmented with a
high precision silicon tracker. We show that the CMS detector will serve as an effective tool to
reconstruct jets in both the calorimeters and tracker and to study medium-induced modifications of
jet properties in heavy-ion collisions.
71
Probing the Quark Gluon Plasma at LHC with virtual
40
γ/Z 0
tagged
Jets in CMS
Camelia Mironov for the CMS Collaboration
Los Alamos National Laboratory, Los Alamos, NM, USA, E-mail [email protected]
One important tool in the study of the Quark Gluon Plasma at RHIC was the measurement of
di-jets investigated via leading hadron correlations. With much higher rates for hard processes at the
Large Hadron Collider, the study of virtual photon tagged jets becomes possible. Instead of
measuring back to back correlations of two strongly interacting particles, one side is replaced by an
electromagnetic probe which propagates through the plasma undisturbed and provides a
measurement of the energy of the initial hard scattering. The experimental signature of the virtual
photon is the measurement of muon pairs, making CMS an ideally suited detector. Moreover the
production of the Z0 boson will be so abundant that the muon pairs from its decay can also be used
as jet tags. We propose to use the lepton pair tagged jets to study medium induced partonic energy
loss and to measure in medium parton fragmentation functions. A background source for the
dilepton jet tag signal is the lepton pairs from the semi leptonic decay of heavy mesons pairs(B/B
and D/D)We present signal rates (simulated with the PYTHIA eventgenerator) and the rates of the
background together with a discussion of strategies to maximize the signal-to-background ratio.
72
ENERGY LOSS OF A HEAVY QUARK PRODUCED IN A
FINITE SIZE MEDIUM
P.B. GOSSIAUXa, J. AICHELINa, C. BRANDTa and S. PEIGNEa,b
UMR 6457, Universit´e de Nantes, Ecole des Mines de Nantes, IN2P3/CNRS, 4 rue
Alfred Kastler, 44307 Nantes cedex 3, France. [email protected]
bOn leave of absence from LAPTH, CNRS, UMR 5108, Universit´e de Savoie, B.P. 110,
F-74941, Annecy-le-Vieux Cedex, France.
aSUBATECH,
We study the medium-induced energy loss −∆E0(Lp) suffered by a heavy quark produced at
initial time in a quark-gluon plasma, and escaping the plasma after travelling the distance Lp. The
heavy quark is treated classically,and within the same framework −∆E0(Lp) consistently
includes:the loss from standard collisional processes, initial bremsstrahlung due to the sudden
acceleration of the quark, and transition radiation (novelty as compared to [1]). The radiative loss
induced by rescatterings −∆Erad(Lp) is not included in our present study. For a ultrarelativistic
heavy quark with momentum p ∼ 10 GeV, and for a finite plasma with Lp ∼ 10 fm, the loss
−∆E0(Lp) is strongly suppressed compared to the standard stationary regime −∆E0(Lp) −∆Ecoll
(Lp)q ∝Lp valid when Lpbecomes large, although the transition radiation partly reduces this
suppression. Physically, the suppression is a consequence of the retardation effect [1] affecting
collisional processes - the latter cannot start at initial time when the heavy quark has not built its
asymptotic proper field yet.Our results indicate that −∆E0(Lp) should be the dominant contribution
to the total heavy quark energy loss −∆Etot = −∆E0 − ∆Erad
−∆Erad, as indeed assumed in most of
jet-quenching analyses. However they might raise some question concerning the RHIC data on
large p⊥ electron spectra.
References
[1] S.Peigne, P.B.Gossiaux and T.Gousset,Retardation effect for collisional energy loss of hard partons
produced in QGP'', J. High Energy Phys. JHEP04(2006)011 [hep-ph/0509185].
73
HEAVY QUARK ENERGY LOSS DUE TO THREE-BODY
SCATTERING IN A QUARK-GLUON PLASMA
C. M. Koa and W. Liub
Institute and Physics Department, Texas A&M University
College Station, Texas 77843-3366, USA, [email protected]
bCyclotron Institute and Physics Department, Texas A&M University
College Station, Texas 77843-3366, USA, [email protected]
aCyclotron
Heavy quark three-body scattering in a quark-gluon plasma is studied in the lowest order in
Quantum Chromodynamics. To gauge its effect relative to that due to two-body elastic and radiative
41
scattering,its contribution to the drag coefficient in the Fokker-Planck description of heavy quark
diffusion in the quark-gluon plasma is evaluated. For heavy quark scattering by two quarks and
antiquarks,we have calculated all allowed lowest-order diagrams and found that it is dominated by
those with two gluons attached to the heavy quark after including thermal masses for time-like
partons and screening masses for space-like partons. Considering only diagrams with two gluons
attached to the heavy quark, we have extended the calculation to heavy quark scattering by a
quark-gluon pair or two gluons. Our results show that for both charm and bottom quarks, the
contribution from three-body scattering to their drag coefficients in the quark-gluon plasma is larger
than those due to two-body elastic scattering. Compared to two-body radiative scattering,
three-body scattering gives a larger contribution at lower transverse momentum but a smaller
contribution at high transverse momentum. The transverse momentum at which the relative
importance between three-body scattering and two-body radiative scattering changes their order is
larger for the bottom quark than for the charm quark. Using a schematic expanding fireball model,
effects of both two-body and three-body scattering on the transverse momentum spectra of heavy
quarks produced in Au+Au collisions at center of mass energy
=200 GeV are studied.
Results on electrons from resulting heavy meson decays are compared with available experimental
data [1].
References:
[1] W.Liu and C.M.Ko, nucl-th/0603004.
74
Jet energy loss at RHIC and LHC, including collisional and radiative mechanisms and
fluctuations
S. Wicksa,W. Horowitzb and M. Gyulassyc
of Physics, Columbia University, 538 W. 120th St, New York, NY 10025, USA,
[email protected]
[email protected]; [email protected]
It has been shown that perturbative QCD radiative energy loss alone cannot account for the
observed suppression of (single non-photonic) electrons at RHIC. The situation significantly
improves if collisional energy loss is also included. The combination of radiative and collisional
energy losses further affects predictions for jet suppression at the LHC. A full treatment of
fluctuations in the energy loss is essential to making consistent predictions for RAA(pT ) for all quark
flavours and products at both experiments. This includes variation in the number of collisions and
gluons emitted, the distribution of energy loss in each collision or gluon emission, as well as
variation in the path lengths traversed by the jets.
References
[1] S.Wicks, W.Horowitz, M.Djordjevic, and M.Gyulassy, nucl-th/0512076
75
Heavy quark energy loss and the non-photonic electron spectrum
Li Shi-Yuana,b, Wang En-Keb, Wang Xin-Niana,b,c and Yao Taoa
Jinan, Shandong, 250100, P. R. China, [email protected]
bInstitute of Particle Physics, Huazhong Normal University
Wuhan, Hubei, 430079, P.R. China
cNuclear Science Division, MS 70R0319, Lawrence Berkeley National LaboratoryBerkeley,
CA 94720 USA
Employing the ZWW [1] framework of heavy quark energy loss and the modified
fragmentation function, we calculate the non-photonic electron (i.e., the electron fromheavy quark
decay) transverse momentum spectrum as well as the nuclear suppression Rcp in AA collision at
RHIC. In the same framework, with quark mass MQ → 0, we investigate the light quarkenergy
loss and fit the results to the experimental data to fix parameters.The uncertainty of the electron
spectrum from the relative production rates between heavy mesons and baryons is also
investigated, taking advantage of the combination model.
42
References
[1] Ben-Wei Zhang, Enke Wang and Xin-Nian Wang, Nucl. Phys. A 757: 493, 2005.
76
JET SHAPES IN OPAQUE MEDIA
Dipartimento di Fisica, Universita di Roma “La Sapienza” and INFN, Roma, Italy,
[email protected]
One of the most striking observation made at RHIC in the last years is the atypical
non-gaussian shape of the away-side azimuthal correlation of high-pt particles.We show that,
without invoking new mechanisms, these non-gaussian shapes find a natural explanation within the
usual approach to jet quenching, namely the radiative energy loss. The central point of our
argument is the need of a more exclusive treatment of the distributions to describe experimental
data with restrictive kinematical constrains.We propose a rather simple generalization of the
Sudakov form factors, following the well-known case of parton showers in vacuum, to build such
exclusive distributions. In the case that the measured data is dominated by a small number of
splittings, we find a double-peak structure with the position of the maxima in agreement with the
centrality dependence measured experimentally. We show, in this way, that non-trivial angular
dependences appear naturaly within the perturbative treatment of jet quenching for very opaque
media, characterized by a large ∼10 GeV2 /fm Hence, a framework for a unified description of
medium effects in high-pt particles is provided by the medium--induced gluon radiation formalism.
References
Base on:[1] A.D.Polosa and C.A.Salgado,Jet shapes in opaque media,arXiv:hep-ph/0607295.
77
Can collisional energy loss explain nuclear suppression factor for light hadrons
Abhee K. Dutt-Mazumderb, Pradip K. Royb and Jan-e Alama
a Variable Energy Cyclotron Centre, /AF, Bidhan Nagar Kolkata 700 064,
[email protected]
bSaha Institute of Nuclear Physics, Physics /AF, Bidhan Nagar Kolkata 700 064, India
Average energy loss of light quarks has been calculated in a two stage equilibrium scenario
where the quarks are assumed to execute Brownian motion in a gluonic heat bath [1].The evolution
of the quark pT spectra is studied by solving Fokker-Planck equation in an expanding plasma.At the
transition temperature, Tc∼170MeV , the transverse momentum distribution of pions have been
calculated [2] through the fragmentation of the evolved partons.The nuclear suppression factor for
pions has been estimated and compared with experimentally measured pion pT spectrum at RHIC.
References
[1] P. Roy, A. K. Dutt-Mazumder and J. Alam,Phys. Rev. C 73, 044911 (2006).
[2] J. Alam, P. Roy and A. K. Dutt-Mazumder, hep-ph/0604131.
78
A Next-to-Leading-Order Analysis of Jet Quenching
in High Energy A + A Collisions
Hanzhong Zhang
Institute of Particle Physics, Central China Normal University
Wuhan, 430079, P. R. China, [email protected]
Co-authors: Jeff Owens, Enke Wang , Xin-Nian Wang
One of the most exciting phenomena observed in heavy-ion collisions in the last years is jet
quenching[1]—If a dense partonic matter is formed during the initial stage of a heavy-ion collision
with a large volume and a long life time (relative to the confinement scale 1/ΛQCD),the produced
large ET parton will interact with this dense medium and will lose its energy via induced gluon
Within a Next-to-Leading-Order (NLO)[2] pQCD parton model, we analyze numerically the
43
single hadron and dihadron productions in Au + Au, C u + C u collisions at 63, 200 GeV and in P b
+ P b collision at 5.5 TeV. Theoretical calculations in Au + Au collisions at 63 and 200 GeV are
compared with RHIC data[3]. Because of 2 → 3 subprocess, there are much more gluon jets in
NLO comparing to the LO (Leading-Order) case. Gluon jet loses more than 2 times energy compare
to quark jet, so NLO results show stronger quenching effect than LO results. With jet quenching
effects taken into account, the nuclear modification factor RAA, IAA and elliptical flow papameter
v2 from the NLO calculation fit data well.
These results provide further evidences of jet quenching discovered in heavy ion collisions
which include the suppression of single hadron pT spectra and dihadron M spectra, high-pT
azimuthal anisotropy and back-to-back correlations in high-energy heavy-ion collisions
incorporating current theoretical understanding of parton energy loss. Furthermore, we give the
prediction on single hadron and dihadron productions in P b + P b collisions at 5.5 TeV.
References
[1]M.Gyulassy and X.-N.Wang,Nucl. Phys. B420, 583 (1994); X.-N.Wang, M. Gyulassy and M.Plu¨mer,
Phys.Rev.D51,3436(1995);E.Wang and X.-N.Wang, Phys. Rev.Lett.87,142301 (2001); Phys.Rev.Lett. 89,
162301(2002).
[2] R.K.Ellis and J.C.Sexton, Nucl.Phys.B269(1986)445; J.F. Owens, Phys. Rev.D65,034011(2002);
B.W.Harris and J.F.Owens, Phys.Rev.D65,094032(2002).
[3] C. Adler et al., Phys.Rev.Lett.91, 241803(2003); Stefan Bathe U C Riverside
for PHENIX Collaboration DNP/JPS 2005,September 20;David L.Winter for PHENIX Collaboration CIPANP
2006,May 30-June 3; D.d’Enterria, Eur.Phys.
J. C 43,295-302(2005); Henner Busching for PHENIX
Collaboration, J.Phys.G 31 (2005)S473-S480.
[4] Xin-Nian Wang, Zheng Hueng and Ina Sarcevic, Phys. Rev. Lett. 68, 231(1996); Phys.Rev.C55, 3047(1997);
Xin-Nian Wang, Phys. Lett. B 595(2004)165-170.A Next-to-Leading-Order Analysis of Jet Quenching
79
ALTERNATIVE VIEW ON JET ABSORPTION CENARIO
V. S. Pantuev
Department of Physics and Astronomy, The University at Stony Brook
Stony Brook, New York, 11794-3800, USA, [email protected]
The study of energy loss of high pt partons is often called ’jet tomography’ of high-density
state of relativistic heavy ion collisions. From the experimental point of view it relies on
observations such as nuclear suppression of inclusive high pt hadrons, partial disappearance of
di-jet events, investigation of jet suppression versus angle with respect to the reaction plane. Also,
the measurement of large anisotropy for high pt particle v2, is an additional tool of jet tomography.
Theoretical interpretation of all these experimental observables is still incomplete and sometimes contradictory. The nuclear modification factor, Raa, which is used to quantify nuclear
suppression, was described by a variety of models, although some of these models use very
different initial assumptions. It seems that Raa by itself cannot provide enough detailed
information. On the other hand, although, most of alculations agree on Raa, they fail to reproduce
the v2 value at high pt or the magnitude of di-jets event. Furthermore, none of the existing models
seriously try to describe the ever more sensitive ”repackaging” of the v2- reaction plane dependence
of Raa - a new ’jet tomography’-type result obtained recently by PHENIX collaboration [1].
Surprisingly, all of the mentioned experimental data could be described by a very simple
assumption of jet production purely from corona region of two overlapping nuclei with a very
opaque core [2]. The only difference from other models with opaque core and trans- parent halo is
that we allow jets free streaming in all transverse directions for some time of about 2 fm/c. The
obtained Raa value has a very little sensitivity to details of the actual jet absorption but is
determined solely by the retarded jet absorption time. Time-space duality of a such assumption
produces a deeper corona region for the jet and di-jet production, it explains v2 at high pt, Raa, and
its dependence versus angle in the reaction plane.
This could be a hint on a new feature of the strongly interacting QGP. Intuitively, the rea- son
for ’delayed’ jet absorption could be non-trivial response of strongly interacting plasma to fast
moving color charge at early stages of plasma, or maybe, quasi-bound states of quasi-particles,
44
which will need some latent time, play the dominant role in jet quenching. The absence of jet
absorption at early stages of the collision presents an alternative to the paradigm of pQCD parton
energy loss models.
References
[1] D. Winter, for the PHENIX collaboration, e-print arXiv nucl-ex/0511039.
[2]V. S. Pantuev, e-print arXiv hep-ph/0506095.ALTERNATIVE VIEW ON JET ABSORPTION SCENARIO}
80
Finite Creation Time Effects on Collisional Energy Loss of
Non-Asymptotic Jets in a QGP
A. Adil a , M. Gyulassy a , W. A. Horowitz a and S. Wicks a
Columbia University, Department of Physics,538 West 120th street
New York, NY 10027. USA, [email protected]
a
We calculate the collisional energy loss suffered by a heavy (charm) quark created at a finite
time within a Quark Gluon Plasma (QGP) in the classical linear response formalism as in Peigne et
al. [1]. We pay close attention to the problem of formulating a conserved current and accounting for
both binding and radiative energy loss effects. We find that binding effects in particular are large
and need to be treated using a ‘modified’ field prescription instead of the conventional induced field.
We find that the finite time correction is on the order of a Debye length as expected and the overall
energy loss is similar in magnitude to the energy loss suffered by a charge created in the asymptotic
past. This result has significant implications for the relative contribution to energy loss from
collisional and radiative sources and will have ramifications for the “single electron puzzle” at
RHIC as well as other experimental observables. The presentation is based on work detailed in [2].
References
[1] T. Sawyer, M. Twain, and I.M. Yu, International Journal of Experimental Physics , v. 97,p. 229-256, 1994.
[2] A. Adil, M. Gyulassy, W. A. Horowitz, and S. Wicks, arXiv:nucl-th/0606010..
81
Effect of jet quenching on the hydrodynamical evolution of QGP
A. K. Chaudhuri a and U. Heinz b
a) Variable Energy Cyclotron Centre, 1-AF, Bidhan Nagar, Kolkata 700 064, India,
[email protected]
b) Department of Physics,The Ohio State University,Columbus, OH 43210, USA,
[email protected]
In jet quenching [1], a QCD jet, before fragmenting in to hadrons, deposits a fraction of its
energy in the medium. As a result, at the time of fragmentation to hadrons, the partons have less
energy and consequently will produce less hadrons than would have otherwise. The model explains
the high pT suppression observed in RHIC Au+Au collisions.
A QCD jet moves nearly at the speed of light cjet ≈1. The speed of sound in QGP is c∽1/3, is
much less than the jet speed. The motion of a QCD jet through the QGP then can produce shock
waves. Shock waves are produced as density perturbations created by a supersonic source. A
fraction of the density perturbations get accumulated in a Mach cone, with Mach angle
. We have simulated the evolution of a QGP fluid with a quenching jet [3]. Initial
conditions of the fluid approximately correspond to Au+Au collisions at RHIC energy. Assuming
that the quenching jet acts as a current source, boost-invariant hydrodynamical equations are solved.
The resulting evolution of the energy density of the QGP fluid indicate that for parton energy loss
consistent with observed high pT suppression, the effects of the energy deposition from the fast
parton are not large. Only for a much larger energy loss a clear conical flow pattern emerges. The
accumulating wave fronts from the expanding energy density waves build up a sonic boom'' shock
front which creates a Mach cone. The cone normal vector forms an angle θM with the direction of
the quenching jet that is qualitatively consistent with expectations from the theoretical relation
. However, this angle is not sharply defined since the cone surface curves due to
inhomogeneity and radial expansion of the underlying medium. This differs from the static
45
homogeneous case. Furthermore, a variety of simulations has shown that the conical structure seen
in the energy density contours is not recognizable in the azimuthal angular distribution of emitted
pions. Other angular effects, such as backsplash from the fireball surface into the direction of the
trigger particle, overlay the Mach cone structure. In none of the cases studied we find peaks at the
predicted Mach angle with an associated dip in the direction of the quenched jet at Ф=π.
References:
1. X. N. Wang and M. Gyulassy, Phys.Rev. Lett. 68 (1992) 1470.
2. J. Casalderrey-Solana, E. V. Shuryak and D. Teaney, hep-ph/0411315.
3. A. K. Chaudhuri and U. Heinz, Phys. Rev. Lett. (in press); nucl-th/0503028.
82
JETS IN HEAVY ION COLLISIONS WITH A FAST KT JET-FINDER
Matteo Cacciari and Gavin P.Salam
LPTHE (CNRS UMR 7589, Universit\'e Pierre et Marie Curie -- Paris 6;
Universit\'e Denis Diderot -- Paris 7; Paris 75005, France.
[email protected], [email protected]
Jets have never been observed so far in heavy ion collisions, due to the difficulty of extracting
them from the huge background. We propose the use of a sequential recombination jet-finder (such
as the kt jet finder) for this task. Such jet-finders are favoured in QCD because of their ability to
approximately invert the QCD branching sequence. Their use in high multiplicity environments
has so far been hindered by issues of speed (they were thought to take a time proportional to the
cube of the number of particles) and the background subtraction. This talk will discuss major
progress which has been made on both these issues recently [1,2]. First studies suggest that a
meaningful inclusive-jet cross section might be measured down to transverse momenta as low as 30
GeV in Pb-Pb collisions at the LHC.
References:
[1] M.Cacciari and G.P.Salam, Dispelling the N3 myth for the k(t) jet-finder,'' hep-ph/0512210.
[2] Talk by M.Cacciari at http://ph-dep-th.web.cern.ch/ph-dep-th/workshops/mc4lhc06/; M.Cacciari and
G.P.Salam, in preparation.
83
NUMERICAL EVALUATION OF JET ENERGY LOSS
B. Betza, K. Paechb, D. H. Rischkec and H. Stockerd
Institute for Theoretical Physics, Max-von-Laue-Stra_e 1, Johann Wolfgang Goethe-University,
Frankfurt, 60438, Germany, [email protected]
b Departement of Physics and Astronomy, Michigan State University, East Lansing,
Michigan,48824-1321, USA, [email protected]
c Institute for Theoretical Physics and Frankfurt Institute for Advanced Science (FIAS)
Max-von-Laue-Stra_e 1, Johann Wolfgang Goethe-University, Frankfurt, 60438
Germany, [email protected]
d Institute for Theoretical Physics and Frankfurt Institute for Advanced Science (FIAS)
Max-von-Laue-Stra_e 1, Johann Wolfgang Goethe-University, Frankfurt, 60438
Germany, [email protected]
a
An aspect of high-energy nuclear collision that has been under vigorous debate recently
concerns the quenching of jets by the expanding hot and dense medium. Experimental data show an
anomalous behaviour in the angular distribution of the particles created in the jet. It is assumed that
it reects the interaction of the jet with the medium [1]. However, it is not entirely clear how the jet
interacts with the medium and therefore the first step would be to study two different scenarios
within an ideal (3+1)d hydrodynamics approach [2]:
1) the jet continously deposits energy and momentum to the medium,
2) the jet deposits most of its energy and momentum during a very short time in a small spatial
volume.
In both scenarios the medium will strongly depend on the underlying equation of state and
therefore will inucence the evolution of the jet through the medium.
References:
46
[1] M. Gyulassy, P. Levai and I. Vitev, Nucl. Phys. B 594, 371 (2001); H. St•ocker, Nucl. Phys. A 750 (2005)
121; F. Antinori and E. V. Shuryak, J. Phys. G 31, L19 (2005).
[2] D. H. Rischke, S. Bernard and J. A. Maruhn, Nucl. Phys. A 595, 346 (1995).
84
A model of jet quenching in ultrarelativistic heavy ion collisions and high-pt hadron
spectra at RHIC
I.P.Lokhtin
M.V. Lomonosov Moscow State Univ., D.V. Skobeltsyn Inst. Of Nucl Phys, 119992, Vorobievy Gory,
Moscow, Russia
One of the important tools to study properties of quark-gluon plasma (QGP) in heavy ion
collisions is a QCD jet production. In order to test the sensitivity of experimental observables to
QGP formation, the creation of adequate fast Monte-Carlo tools is necessary. We have developed
the model to simulate jet quenching in ultrarelativistic heavy ion collisions. It includes the
generation of the hard parton production vertex according to the realistic nuclear geometry,
rescattering-by-rescattering simulation of the parton path length in a dense matter, radiative and
collisional energy loss per rescattering, final hadronization with the Lund string fragmentation
model for hard partons and in-medium emitted gluons. The model is the fast Monte-Carlo tool
implemented to modify a standard PYTHIA jet event. The model has been generalized to the case
of the full'' heavy ion event (the superposition of soft, hydro-type state and hard multi-jets) using a
simple and fast simulation procedure for soft particle production.
The efficiency of the model is demonstrated basing on the numerical analysis of
high-$p_T$ hadron production in Au+Au collisions at RHIC. The good fit of experimental data on
$\eta$-- and $p_T$-- spectra of hadrons for different event centralities is achieved. The model is
capable of reproducing main features of the jet quenching pattern at RHIC: the $p_T$ dependence
of the nuclear modification factor $R_{AA}$, and the suppression of azimuthal back-to-back
correlations. The applications of the model to analyze jet quenching in various new channels at
LHC energy (jets tagged by leading particles, dilepton-jet correlations, energy-energy correlations,
etc.) are discussed.
[1] I.P. Lokhtin and A.M. Snigirev, \textit{European Physical Journal\/}, v.~C 45, p.~211-217, 2006.
85
The QCD collisional energy loss revised
A. Peshiera
fu¨r Theoretische Physik, Universita¨t Giessen
D-35392 Giessen, Germany, [email protected]
aInstitut
Recent dedicated studies indicate that, besides radiation, a collisional contribution to the
partonic energy loss is important to describe the available jet quenching data. All these
considerations have been based on Bjorken-type formulae,
I will
show first that this formula is inappropriate/incorrect. In the discussion of the collisional energy loss,
loop corrections to the tree level approximation are essential -- which yields [1]
Within this novel framework, I calculate the collisional {\em quenching
weights} and implement a dynamic-probabilistic Monte Carlo model of jet quenching [2]. The
results demonstrate that the effect of collisions is indeed sizable -- which sheds new light upon the
interpretation of RHIC data.
References:
[1] A. Peshier, hep-ph/0605294.
[2] A. Peshier, hep-ph/0607299.
86
Flow Coefficients and Jet Characteristics in Heavy Ion Collisions
47
Sadhana Dash, Dipak K. Mishra, S. C. Phatak and P. K. Sahu
Institute of Physics, Bhubaneswar 751 005, India
Identifying jets in heavy ion collisions is of significant interest since the prop- erties of jets are
expected to get modified because of the formation of quark gluon plasma[1-3]. The detection of jets
is, however, difficult because of large number of non-jet hadrons produced in the collision process.
In this work we propose a method of identifying and determining the transverse momentum of jets
by means of flow analysis. The expression for pT -weighted flow coefficientsis given by
where
is the average transverse momentum carried by a hadron in the
jet. Thus
is the transverse momentum of the jet.
If one plots  m2 and m2 , pT vs  m2 ,the points would lie on a straight line. The intercept of the line
will yield the number of jet particles and the pT of the jet respectively ( since N , the total number of
particles is known ). And from the slope, one can determine σ or ∆φ.So, the procedure is to fit a
straight line to the computed flow coefficients and determine the intercept and slope. These in turn
would yield number of jet particles, jet transverse momentum and jet opening angle.
References
[1] X.N.Wang and M.Gyulassy,Phys.Rev.Lett. 68,1480 (1992).
[2] M. Gyulassy, I. Vitev and X. -N. Wang, Phys. Rev. Lett. 86, 2537 (2001).
[3] S. C. Phatak and P. K. Sahu, Phys. Rev. C 69, 024901 (2004)Flow Coefficients and Jet Characteristics in
Heavy Ion Collisions}
87
The fate of the Mach cone in covariant transport theory
Denes Molnar (Purdue University, U.S.A.)
It has been argued that the remarkable two tiny "ears" on the away-side in the azimuthal
correlation between a high-pT jet trigger and a lower-pT associated particle observed at RHIC may
be indicitive of hydrodynamic Mach shocks in dense quark-gluon matter. However, a recent ideal
hydrodynamic calculation by Chaudhuri and Heinz found (albeit resctricted to 2+1 dimensions) a
rather different correlation pattern with a single,small away-side peak. That study, on the other hand,
neglects dissipation due to viscosity, which damps hydrodynamic waves substantially.Dissipative
effects are naturally included in transport models (due to finite scattering rates), and are expected to
weaken Mach cone signatures.Surprisingly, a calculation by Ma et al using the AMPT transport
model found significant "Mach-cone"-like structures in the two-particle azimuthal
correlations.Unfortunately, AMPT - though motivated by the covariant Boltzmann equation is not
Lorentz covariant because its naive cascade algorithm allows acausal (superluminal) signal
propagation. Such artifacts are known to affect various observables at RHIC, such as spectra,
elliptic flow, and spacetime distributions at freezeout. In this talk I present results on the fate of the
Mach-cone from the covariant MPC transport model, and discuss the role of dissipation in this
observable.
88
AdS/CFT and physics of heavy ion collisions
Hong Liu
Center for Theoretical Physics, Massachusetts Institute of Technology
Cambridge, MA 02139, USA, [email protected]
The AdS/CFT correspondence, which maps certain gauge theories to a gravity theory,
provides important avenues for understanding the dynamics of strongly coupled gauge theories. The
techniques o®ered by the correspondence are particularly valuable for extracting qualitative
information about those physical quantities in QCD which are not directly available from lattice
calculations, such as transport coe±cients, or dynamical processes of any sort. Thus the AdS/CFT
48
correspondence has potential for providing important insights into the physics of heavy ion
collisions at RHIC or LHC. I will describe two lines of recent research activities in applying
AdS/CFT to heavy ion collisions led by [1] and [2].
The first concerns calculating the “jet quenching parameter” q in various strongly coupled
gauge theories. It was found that in hot
= 4 supersymmetric QCD,
q
SYM
=
in the limit in which both Nc and
are large. A few other
strongly coupled gauge theories (with varying number of supersymmetries and matter contents)
studied so far yielded qualitatively similar behavior. These studies suggest that q is not
proportional to the entropy density, or to some \number density of scatterers" as is usually assumed
in the literature. The second line of research concerns understanding the screening length Ls for a
heavy quark-antiquark pair moving with a velocity v in the \quark-gluon" plasma of various
strongly coupled supersymmetric gauge theories. It was found that for conformal theories
1
2 4
Ls  (1  v )
as v  1 with only mild dependence on the direction of v.
Since in a heavy ion
collision a cc pair is produced with some randomly directed initial transverse velocity, within a
hot fluid that itself subsequently develops strong collective flow, such velocity scaling of the
screening length could provide insights into the J/ suppression in heavy ion collisions at LHC.
References:
[1] H. Liu, K. Rajagopal and U. A. Wiedemann, “Calculating the jet quenching parameter
from AdS/CFT," hep-ph/0605178; to appear in Phys. Rev. Lett.
[2] H. Liu, K. Rajagopal and U. A. Wiedemann, “An AdS/CFT calculation of screening in a hot wind,"
hep-ph/0607062; submitted to Phys. Rev. Lett.
89
Near-side ∆η correlations of high-pt hadrons from STAR
Jorn Putschkea for the STAR collaboration
Lawrence Berkeley National Laboratory
Berkeley, California, 94720, US, [email protected]
a
Systematic measurements of pseudorapidity (∆η) and azimuthal (∆φ) correlations between
high-pt charged hadrons and associated particles from the high statistics 200 GeV Au+Au and
Cu+Cu datasets will be presented. In previous measurements differences in the near- side ∆η
correlation between central Au+Au and the lighter systems d+Au and p+p were observed, including
an additional long-range near-side correlation (ridge) in Au+Au collisions. A detailed
characterization of the near-side correlated yield in both the ridge and the jet component as a
function of trigger and associated particle pt will be presented. Results with identified associated
protons and pions will also be shown. These measurements will help distinguish various models for
the origin of the ridge, such as coupling of induced radiation to longitudinal flow [1], a combination
of jet-quenching and strong radial flow [2] or recombination of thermal partons [3].
References:
[1] N. Armesto, et al. , Phys. Rev. Lett. 93, 242301(2004), hep-ph/0405301.
[2] S. A. Voloshin, Nucl. Phys. A 749, 287290(2005), nucl-th/0410024.
[3] C. B. Chiu, and R. C. Hwa, Phys. Rev. C 72, 034903(2005), nucl-th/0505014.
90
Mechanism of Particle Production in p+p and d+Au collisions
Pawan Kumar Netrakanti (For STAR Collaboration)
Variable Energy Cyclotron Center, 1/AF Bidhan Nagar
Kolkata, West Bengal, 700064, India, [email protected]
We present the measurement of identified hadron (π±, K ±, p, p , Λ,  , Ξ± and Ω±) pT
spectra up to pT < 10 GeV/c at midrapidity in p+p and d+Au collisions at √sN N = 200 GeV in the
STAR experiment at RHIC. Through these measurements and comparison to models, we discuss the
49
various aspects concerning the mechanism of particle production and specifically study the
hadronization of partons to hadrons. Our results in p+p collisions demand re-tuning of the default
baryon production parameters in Leading-order (LO) models using string fragmentation, such as
PYTHIA. Our data is also compared with Next-to-Leading (NLO) order pQCD calculations using
parameterized, flavor-separated fragmentation functions for quarks and gluons. We find the need for
a higher contribution from gluon fragmentation to baryon production[1]. This is further
corroborated by the first time observation of a baryon-meson splitting in mT-scaling in both p+p
and d+Au collisions at high pT . The identified particle nuclear modification factor in d+Au
collisions for various hadrons will be presented. A more differential measurement, the ratio of
identified particle production in the forward and backward rapidity in the rapidity region |y|<1, as a
function of pT, called as rapidity asymmetry (YAsym), is used to understand the relative
contribution of different mechanisms (e.g multiple scattering, energy loss in cold nuclear matter,
nuclear shadowing, saturation effects and recombination) to particle production at high pT in d+Au
collision. The particle ratios measured in d+Au and p+Au (selected via neutron-tagging) show
sensitivity to the valence quark fragmentation and can be used to study the quark and gluon
contributions to hadrons production at high pT .
References:
[1] STAR Collaboration, J. Adams et al., Physics Letters B , v. 637, p. 161-169, 2006.
91
Properties of particle production at large transverse momenta in Cu+Cu and
Au+Au collisions at RHIC energies
Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata - 700064, India,
[email protected]
Studying the incident energy and system size dependence of various particle species over an
extended momentum range provides a sensitive experimental tool for investigating energy loss
mechanisms in the medium created in nucleus-nucleus collisions at RHIC and the path length
effects on energy loss. It also allows to address details of baryon transport and the origin of baryon
to meson enhancement in the intermediate pT (2 < pT < 6 GeV/c) region. In this talk we present the
√sNN and system size dependence of the pT spectra for identified charged pions, protons and
anti-protons using Cu+Cu system and Au+Au collisions at √sNN = 62.4 and 200 GeV. The
midrapidity spectra obtained with STAR Time Projection Chamber and Time Of Flight detectors are
measured over the momentum range of 0.2 <pT < 10 GeV/c. Through these measurements we
conduct a systematic study of the inter- play between fragmentation and non-fragmentation
contributions to the particle production, addressing specifically:
System size effects on energy loss for different color-charge partons, the life time ofthe dense
matter formed, and study the energy dependence of parton energy loss and initial jet spectra,
Specific predictions from the quark coalescence models regarding energy dependence of baryon
enhancement in the intermediate pT region, and Results on the xT scaling of pions and protons to
look for violations due to medium induced gluon radiations and recombination processes.
92
NUCLEAR-INDUCED PARTICLE SUPPRESSION AT LARGE xF AT RHIC
J.H. Leea for the BRAHMS Collaboration
of Physics, Brookhaven National Laboratory,Upton, NY 11973, U.S.A., [email protected]
The available kinematic phase-space at large Feynman-x (xF) demands the probability of
particle production to be constrained. In the nuclear medium, the effect is expected to be enhanced
by multiple interactions given to the projectile parton. This effect, referred to as the Sudakov
suppression [1] is exhibited to be scaled with xF. To understand the dynamic nature of nuclear
collisions, it is important to distinguish such kinematically dominated effects from dynamically
driven processes, such as parton energy loss in the hot nuclear medium and gluon saturation in the
initial state. The BRAHMS experiment have measured centrality dependent particle productions in
50
wide kinematic ranges (0.3<pT <2.5-4 GeV/c,0<xF<0.4-0.9) in d+Au, Au+Au, and Cu+Cu at
sNN =200 and 62.4GeV at RHIC. The xF -dependent nuclear modification factors of negative
hadron yields will be presented in the context of parton energy loss [2], gluon saturation [3], and
energy conservation in the medium.
References
[1] B.Z. Kopeliovich et al.,Phys.Rev. C 72 (2005) 054606.
[2] M. Gyulassy et al., arXiv:nucl-th/0302077, and references therein.
[3] L. McLerran and R. Venugopalan, Phys. Rev. D 49 (1994) 2233
93
Low- and intermediate-pT azimuthal di-hadron correlations from
collisions measured in STAR.
sNN = 200GeV AuAu
M.J. Hornerab for the STAR Collaboration.
Nuclear Science Division, Lawrence Berkeley National Laboratory Berkeley, California, 94720, USA,
[email protected]
bUCT-CERN Research Centre, Physics Department University of Cape Town, Rondebosch, Western
Cape, 7701, South Africa
a
Low- and intermediate-pT di-hadron correlations have already been used to uncover novel and
exciting results at RHIC, tying together hard processes with bulk properties. Using the full Run IV
high statistics dataset, we present systematic studies of di-hadron correlations for various trigger pT
selections, starting in the coalesence dominated region and extending up into the domain of
fragmentation dominated triggers. By studying these selections as a function of centrality we vary
the in-medium path lengths traversed by the hard partons, providing an additional systematic to
discriminate different contributions. In addition we study the associated pT dependence to
distinguish between various radiative and hydrodynamic scenarios. A first study of near-side,
long-range ∆η correlations at low-pT is also presented. These studies probe the significance of
hydrodynamic, coalescence/recombination and radiative contributions to the correlation shapes as
the contributions vary with pT and centrality and need to be considered simultaneously to describe
correlation shapes. The only way to de- convolute contributions is to study di-hadron correlations as
differentially and systematically as possible.
The complete set of systematic results are discussed in light of the interplay between radiative,
hydrodynamic and recombination scenarios, placing significant constraints on complete theoretical
treaments of energy loss and bulk evolution scenarios.
94
Diagnosing energy loss: PHENIX results on high-pT hadron spectra
B. Sahlmuellera, for the PHENIX collaboration
fuer Kernphysik, University of Muenster 48149 Muenster, Germany,
[email protected]
aInstitut
Measurements of particle yields at high transverse momentum at RHIC have shown a strong
suppression of neutral meson and charged hadron yields in central Au+Au collisions at sNN =
200GeV compared to a binary scaled p+p reference. A suppression has also been observed in
Cu+Cu collisions at the same energy, similar in strength to that in Au+Au collisions for an equal
number of participants. The observed suppression has been attributed to the energy loss of partons
in the hot and dense matter created in the collision. The exact suppression mechanism, however,
remains unclear.
PHENIX has measured spectra of π0, η, and non-identified charged hadrons in various collision
systems and at different energies. These measurements can provide important information for
understanding the suppression mechanism at play. In particular, a new 62.4GeV p+p data set is
important as a crucial baseline for understanding particle production in Au+Au and Cu+Cu
collisions at the same energy. New Cu+Cu data at 22.4 GeV and 62.4 GeV complement the existing
data sets and allow a systematic study of the energy and collision species depencence over a broad
51
range, including a comparison with CERN SPS results. We will present the latest results of these
measurements.
95
Study of Parton-Medium Interactions via Two- Three- Particle Jet Correlations in PHENIX
a
Chun ZHANG for the PHENIX collaborationa
Oak Ridge National Lab.Oak Ridge, TN, 37831, US, [email protected]
Jet quenching[1], one of the key pieces of evidence supporting the discovery of strongly
coupled quark-gluon plasma at RHIC, is a result of strong interactions between hard-scattered
partons and the medium created in relativistic heavy ion collisions. Studying the medium
modifications of jets by comparing the jet yield and shape in heavy ion collisions with those in p+p
at different transverse momenta (pT) and collision geometries can help us to answer questions such
as how the energy carried by hard-scattered partons is dissipated in the medium. Experimental
results from RHIC experiments have already shown various in- triguing features of jet modification
[2,3]. Particularly, the double-peaked away-side profile at modest pT in central and mid-central
heavy ion collisions has inspired several very different theoretical scenarios including Bending-Jet
and Color-Cerenkov-Radiation to describe the interactions between partons and the medium.
We use a particle azimuthal correlation technique to construct jet signals statistically. In
two-particle correlations, a high pT trigger particle is used to tag jet events and the near-and
away-side jet shape and yield are studied. In addition, 3-particle correlations, which can more
powerfully test the various novel theories of the double-peaked away-side profile, are also studied.
The PHENIX experiment has collected a large dataset in Au+Au and Cu+Cu that enables us to
systematically scan the jet modification for different pT bins and different collision geometries using
unidentified charged hadrons. In this talk the latest results from these studies will be reviewed and
discussed
References
[1] PHENIX, K. Adcox et. al., Nucl. Phys. A 757, p.184 (2005).
[2] PHENIX, S. S. Adler et. al., Phys. Rev. Lett. v 97, p.052301 (2006).
[3] F. Wang, J. Phys. G 90, p.S1299 (2004).
III.
Strangeness and Heavy Flavor Production
96
Charm-hadron Correlations as a Sensitive Probe for Thermalizationin High-Energy Nuclear
Collisions
Xianglei Zhu
Frankfurt Institute for Advanced Studies, |Office: 02.213, Johann Wolfgang Goethe University,
Max-von-Laue-Str. 1 ,60438, Frankfurt am Main, Germany
In order to study the heavy flavor interactions with the hot/dense medium and understand the
observed non-photonic electron R_aa and v2 data at RHIC, therefore to address the status of early
thermalization in high-energy nuclear collisions, we propose to measure azimuthal correlations of
With the Langevin equation which describes the random walk of heavy quarks in the medium,
we find that the change of the azimuthal correlation due to momentum conservation is sensitive to
the temperature and the drag coefficient. Both parameters are the key properties of the medium. In
addition, with the UrQMD model, we also show that hadronic interactions at the late stage
hadronic interactions cannot significantly disturb the azimuthal correlations of the D-Dbar pairs.
Thus, a dramatic decrease or the complete absence of these initial correlations will indicate the
frequent interactions of heavy-flavor quarks in the partonic stage
97
Competition Between J/ Suppression and Regeneration in Quark-Gluon Plasma
52
L. Yan*, P.F. Zhuang*, N. Xu**
*: Department of Physics, Tsinghua University
**: Nuclear Science Division, Lawrence Berkeley National Laboratory
Heavy flavor and J/ productions are sensitive probes for analyzing the properties of
the hot and dense medium created in high-energy nuclear collisions. In this paper, we
investigate the competition between J/ suppression and regeneration in collisions at RHIC
and LHC energies. The transport equation, with both gain and loss terms that are controlled
by the pQCD processes g+ J/  c+cbar plus the hydrodynamic evolution, is solved in a
self-consistent manner. Elliptic flow v2, average transverse momentum square <pT2>, and
the nuclear modification factor RAA are presented. Compared with the other model
approaches, our results provide the better fit to the recent experimental data. Our findings
are: (i) At RHIC, the continuous in-medium production is very important for J/’s
momentum distributions while the predicted elliptic flow is still dominated by the creation at
initial impact; (ii) At LHC, most of the initially created J/s are suppressed in the medium
and coalescence process becomes the dominated channel for J/ production.
98
Cold Nuclear Matter Effects on J/ Production in p+A, d+Au and A+A Collisions
R. Vogta, M. Leitchb and C. Lourencoc
Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA,
Department of Physics, University of California at Davis, Davis, CA, 95616, USA, [email protected]
b Los Alamos National Laboratory, Los Alamos, NM, USA, [email protected]
c CERN, CH 1211, Geneva, Switzerland, [email protected]
a
We present an overview of cold nuclear matter effects on charmonium production from SPS to
RHIC energies, including nuclear effects on the parton distribution functions and final- state nuclear
absorption. A good understanding of the cold nuclear matter effects already present in the
proton-nucleus (p + A) and d+Au data is crucial to properly account for the corresponding effects
on charmonium production in nucleus-nucleus (A + A) collisions.
We use the RHIC d+Au data as a function of rapidity and centrality as well as fixed- target p+A
data to study these cold nuclear matter effects. The initial-state nuclear effects on the parton
densities and the final-state charmonium absorption by nucleons, obtained by Glauber calculations
employing a nuclear absorption cross section, σabs, are treated as independent processes. Our
calculations show that the mid-rapidity NA50, E866, HERA-B and PHENIX J/ψ data clearly
indicate thatσabs decreases with increasing s NN , implying stronger normal J/ψ nuclear absorption
in A+A collisions at the SPS than so far assumed for absorption alone. We then look at the SPS and
RHIC A + A data, taking these effects into account, and comment on the results.
Finally we stress the crucial role of p+A charmonia measurements and present predictions of cold
nuclear matter effects in high-energy collisions at the LHC, where the modifications of the parton
densities are even more important, given the low values of the parton momentum fractions probed.
Corresponding author: [email protected]
99
Production of strange particles at RHIC via quark recombination
C.B. Yang
Institute of Particle Physics, Hua-Zhong Normal University
Wuhan 430079, P. R. China, [email protected]
The recombination model is applied to the production of K; Φ;Λ and Ω at all pT in central
Au+Au collisions. The thermal-shower component of the recombination is found to be important
for K and Λ, but not forΦ and Ω in the intermediate pT region. The normalization and inverse slope
of the thermal partons in the strange sector are determined by fitting the low-pT data. The peak in the
Λ/K ratio is shown to rise to nearly 2 at pT about 3 GeV/c. The yields for Φ and Ω are suppressed
and the corresponding inverse slope for thermal squark is higher. The contribution from shower s
quarks is found to be unimportant for pT of Φ and Ω up to 6 GeV/c. We give reasons on the basis of
53
the pT dependence that Φ cannot be formed by means of K + K coalescence.
References
[1] J. Rafelski and B. Müller, Phys. Rev. Lett. 48, 1066 (1982).
[2] P. Koch, B. Müller and J. Rafelski, Phys. Rep. 142, 167 (1986).
[3] P. Braun-Munzinger, K. Redlich and J. Stachel, in Quark Gluon Plasma 3, edited by R.C. Hwa and X.-N.
Wang (World Scienti.c, Singapore, 2004), p. 491.
[4] F. Antinori, nucl-ex/0404032, plenary talk at Quark Matter 2004, 17th Int'l Conf. on Ultra Relativistic
Nucleus-Nucleus Collisions (Oakland, CA, January 2004), edited by H. G.Ritter and X. N. Wang.
[5] R. C. Hwa and C. B. Yang, Phys. Rev. C 70, 024905 (2004).
[6] R. C. Hwa, and C. B. Yang, Phys. Rev. C 66, 064903 (2002).
[7] A. Bialas, Phys. Lett. B 442, 449 (1998).
[8] J. Zimányi, T. S. Biro, T. Csörgö and P. Lévai, Phys. Lett. B 472, 243 (2000).
[9] R. C. Hwa and C. B. Yang, Phys. Rev. C 70, 024904 (04).
[10] K. P. Das and R. C. Hwa, Phys. Lett. B 68, 459 (1977).
[11] R. C. Hwa, Phys. Rev. D 22, 1593 (1980).
[12] R. C. Hwa, and C. B. Yang, Phys. Rev. C 67, 034902 (2003).
[13] V. Greco, C. M. Ko, and P. Lévai, Phys. Rev. Lett. 90, 202302 (2003); Phys. Rev. C68, 034904 (2003).
[14] R. J. Fries, B. Müller, C. Nonaka and S. A. Bass, Phys. Rev. Lett. 90, 202303 (2003);Phys. Rev. C 68,
044902 (2003).
[15] R. C. Hwa, and C. B. Yang, Phys. Rev. C 66, 025204 (2002).
[16] R. C. Hwa, and C. B. Yang, Phys. Rev. C 66, 025205 (2002).
[17] D. K. Srivastava, C. Gale, and R. J. Fries, Phys. Rev. C 67, 034903 (2003).
[18] J. Adams et al. (STAR Collaboration), Phys. Lett. B 612, 181 (2005); nucl-ex/0406003.
[19] J. Velkovska (for PHENIX Collaboration), Eur. Phys. J. C43, 317 (2005).
[20] S. Salur (for STAR Collaboration), talk given at QM05
[21] J. Adams et al. (STAR Collaboration), Phys. Rev. Lett. 92, 182301 (2004)
[22] M. A. C. Lamont (for STAR Collaboration), J. Phys. G: Nucl. Part. Phys. 30, S963 (2004).
100
Status ond Comparison of Chemical Freeze-Out Criteria
J.Cleymans a, H. Oeschler b, K. Redlich c, S. Wheaton a
a)
UCT-CERN Research Centre and Department of Physics,
University of Cape Town, Rondebosch 7701, South Africa
[email protected]
b) Institute of Nuclear Physics, Technische Universität Darmstadt,
c) Institute of Theoretical Physics, University of Wroclaw, Pl-45204 Wroclaw, Poland
One of the most remarkable results to emerge from heavy-ion collisions over the past two
decades is the striking regularity shown by particle yields at all energies. This has led to several
very successful proposals describing particle yields over a very wide range of beam energies,
reaching from 1 A GeV up to 200 A GeV, using only one or two parameters. A systematic
comparison of these proposals is presented here. The conditions of fixed energy per particle,
baryon+anti-baryon density, normalized entropy density as well as percolation model are
investigated. The results are compared with the most recent chemical freeze-out parameters
obtained in the thermal-statistical analysis of particle yields. The sensitivity and dependence of the
results on parameters is analyzed and discussed. It is shown that in the energy range above the top
AGS energy, within present accuracies, all chemical freeze-out criteria give a fairly good
description of the particle yields. However, the low energy heavy-ion data favor the constant energy
per particle as a unified condition of chemical particle freeze-out. This condition also shows the
weakest sensitivity on model assumptions and parameters.
101
Strangeness production in Au+Au reactions at 62.4 AGeV
Arsenea for BRAHMS Collaboration
of Physics, University of Oslo, Oslo, 0316, Norway, [email protected]
The measurement of strangeness is a valuable tool for understanding the reaction mechanism of
54
nuclear collisions since all the strange particles need to be created during the reaction. Also,
strangeness enhancement is one of the predicted signals of the QGP. At low SPS energies,
strangeness production (e.g. measured by the K+/π+ ratio) reaches a maximum which suggests some
sort of a transition to a new regime. At these energies statistical models show that the system is at
its maximum baryo-chemical potential. The pbar/p ratio changes dramatically from AGS to RHIC
energies. A similar change of this ratio happens at RHIC energy going from midrapidity to the
fragmentation peak at forward rapidities. In the present work we will discuss the behaviour of the
strangeness production (i.e. K/π ratio) with rapidity (and net-baryon content) in Au+Au collisions at
62.4 AGeV. In this particular reaction, BRAHMS is able to identify particles of up to about 3.5
rapidity units and thereby cover a wide range of pbar/p ratios, including the fragmentation region.
We will show spectra and ratios of identified particles as a function of mT and rapidity.
References:
[1] I. Arsene et al., Quark Gluon Plasma and Color Glass Condensate at RHIC? The perspective from the BRAHMS experiment , Nucl.Phys.A757(2005)1-27.
102
CENTRALITY AND ENERGY DEPENDENCE OF MESON, PROTON AND
HYPERON PRODUCTION
C. Blumea for the NA49 Collaboration
für Kernphysik, University of Frankfurt, Max-von-Laue Str. 1, 60438 Frankfurt am Main,
Germany, [email protected]
a Institut
The NA49 experiment at the CERN SPS has collected data on nucleus-nucleus collisions in the
beam energy range 20A - 158A GeV. We will present new results on the system size dependence of
Λ and Ξ production in A+A collisions at 40A and 158A GeV, as well as on the energy
dependence of (anti-)proton and K0s production. Together with the results for other identified
particles (charged pions and kaons and Φ mesons) and data from the AGS and RHIC, this allows
for a comprehensive study of the energy and system size dependence of various hadronic
observables, with the aim to identify phenomena related to the onset of deconfinement. This
contribution will discuss in detail the variation of transverse as well as longitudinal spectra with
system size and beam energy, observables which are related to the evolution of transverse and
logitudinal expansion of the created fireball and the stopping of the incoming nuclei. Particle yields
will be presented. Especially the new data on the system size dependence of strange particles will
allow to locate the onset of strangeness enhancement by comparing minimum bias Pb+Pb collisions
to lighter systems (Si+Si, C+C) and elementary p+p collisions, measured with the same
experimental setup, as reference. The energy dependence of particle yields will be discussed in the
light of possible indications for an onset of deconfinement and compared to various model
predictions.
103
PRODUCTION OF Φ MESON IN GOLD-GOLD AND P+P COLLISIONS
AT TOP RHIC ENERGY
L. Bravinaa, K. Tywoniuka, Nu Xub and E. Zabrodina
of Physics, University of Oslo, N-0316 Oslo, Norway,[email protected]
bNuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley,CA 94720, USA
The production of Φ mesons in Au+Au and p+p collisions at top RHIC energy is studied within
the microscopic quark-gluon string model. In accordance with the STAR experimental data kaon
coalescence was not considered among the production channels for the Φ. The inverse slope
parameters of the transverse mass distributions, obtained for five different centrality bins, agree
well with those extracted from the STAR data, while the absolute yield of Φ is underestimated by a
factor 2. Different processes responsible for the increase of the Φ production are examined. It
appears that the fusion of strings cannot increase the Φ yield either. Less than 30% of detectable Φ's
experience elastic scattering, this rate is insufficient for the full thermalization of Φ. The directed
flow of Φ at |y|≤ 2 demonstrates strong antiflow behavior, whereas its elliptic flow rises up to about
55
3.5% in the same rapidity interval. As a function of transverse momentum it rises linearly with
increasing pt, in agreement with the STAR data, and saturates at pt > 2 GeV/c.
References:
[1] L. Bravina, L. Csernai, A. Faessler, C. Fuchs, S. Panitkin, Nu Xu, E. Zabrodin, Nuclear
Physics A, v. 715, p. 665- 668, 2003.
[2] E. Zabrodin, L. Bravina, G. Burau, J. Bleibel, C. Fuchs, A. Faessler, Journal of Physics
G, v. 31, p. 995- 999, 2005.
[3] L. Bravina et al., to be published.
104
DOES CHEMICAL EQUILIBRIUM OCCUR WITHIN SMALL CLUSTERS
Krausa, H. Oeschlera and K. Redlichb
[email protected] , [email protected]
b
Institute of Theoretical Physics, University of Wroclaw, Pl-45204 Wroclaw, Poland
[email protected]
aInstitut
The Statistical Model successfully describes particle production in central Au+Au and Pb+Pb
collisions over a wide range of energies. However, in interactions between C+C and Si+Si nuclei,
the yields of strange particles are reduced, even stronger than expected from canonical suppression.
To cope with this deficit, we propose a model with correlated subvolumes. Under the assumption of
local strangeness conservation within these clusters, particle production from Pb+Pb to p+p can be
reproduced consistently. The general parameterization of freeze-out conditions within the Statistical
Model allows for extrapolations in the LHC energy regime. Predictions for various particle ratios in
Pb+Pb collisions are made [1]. Furthermore, specific particle ratios can be pointed out which are
best suited to determine the temperature and the baryon chemical potential experimentally. It will
be shown how cluster formation in Pb+Pb collisions affects the yields. This will be contrasted with
predictions for p+p interactions.
References:
[1] J. Cleymans, I. Kraus, H. Oeschler, K. Redlich and S. Wheaton, arXiv, hep-ph/0604237, 2006.
105
Energy loss of charm quark via dimuon production in Pb-Pb collisions at
s NN =5.5TeV
Ding Hengtonga, Zhou Daicuia
of Particle Physics, Central China Normal University
Wuhan, 430079, P. R. China, [email protected]
aInstitute
Based on the HVQMNR model on heavy flavor production and the BDMPS approach on
parton energy loss, we have investigated the energy loss effect of charm quark on (di)muon spectra
in forward rapidity region covered by ALICE Forward Muon Spectrometer in Pb+Pb collisions at
s NN = 5.5 TeV. Results show that (di)muon spectra are very sensitive to the charm quark energy
loss and can provide valuable information on the energy loss of heavy flavors.
References :
[1]S.S.Adler et al, Phys. Rev. Lett. 96(2006)032301
[2]N.Armesto, A.Dainese,C.A.Salgado and U.A.Wiedemann Phys. Rev. D71(2005)054027
[3]R.Baier, Y.L.Dokshitzer, A.H.Mueller, S.Peigné and D.Schiff Nucl. Phys. B483(1997)291
[4]M.Mangano, P.Nason and G. Ridolfi Nucl. Phys. B373(1992)295
[5]P.Nason, S.Dawson and R.K.Ellis Nucl. Phys. B327(1988)49
[6]P.Nason, S.Dawson and R.K.Ellis Nucl. Phys. B303(1988)607
106
CERES measurement of strangeness production
in central Pb-Au collisions at top SPS energy
ahysikalisches
S. Radomski a and M. Kalisky b for the CERES Collaboration
Institut der Universität Heidelberg, 69120 Heidelberg, Germany,
56
[email protected]
bsellschaft für Schwerionenforschung, 64291 Darmstadt, Germany,[email protected]
The production of kaons and Λ at top SPS energy was studied by the CERES Collaboration.
The analysis used the large statistics of 30 million events of Pb-Au collisions with centrality of
σ/σgeo < 7% collected during the CERN SPS run in October 2000. The strange particles where
indenti¯ed in the invariant mass spectrum of their decay products reconstructed by the radial TPC.
The rapidity range covered is 1.8 < y < 2.6.
The neutral particles were reconstructed using two body decays: K0 s →π+π- and Λ→pπ-. The
combinatorial background was compensated by the large data sample and the measurement could
by performed without topological cuts. For K0 s the acceptance starts at low transverse momentum
and thus the obtained yield is free of extrapolation uncertainty. Charged kaons were reconstructed
using a three body decay topology (τ decay): K+ →π+π+π- and K- →π+π-π-. The analysis of both
charged and neutral kaons allows the checks of the isospin symmetry and gives two measurements
with quite differnt systematic errors The results are compared to NA49 and NA57 data. The CERES
results shed light on the experimental status of strangeness production and possible sources of
current discrepancies. The results are also discussed in the view of the thermal model of hadron
resonance gas. The elliptic flow coefficient has beem studied as a function of transverse momentum
for Λ and K0s and is compared to the results of pions and protons.
107
Charm Quark Thermalization in Quark-Gluon Plasma
Li Yan
Department of Physics, Tsinghua University, Beijing, 100084, P. R. China,
[email protected]
The charm quark thermalization in quark-gluon plasma is investigated by calculating D-meson
distributions in heavy ion collisions at RHIC and LHC energies. In the frame of transport approach
with a temperature dependent relaxation time for charm quarks as the approximate description for
collision interaction, and hydrodynamic evolution for quark-gluon plasma, we solve the coupled set
of equations and calculate D-meson yield, transverse momentum distribution and elliptic flow v2 at
hadronization. By comparison with the RHIC data, we find the charm quarks have the trend to be
thermalized in the hot medium in central collisions.
108
ALICE potential for open heavy-flavour physics
A. Dainese a, for the ALICE Collaboration
Laboratori Nazionali di Legnaro, viale dell'Universitá 2, 35020 Legnaro (Padova), Italy,
[email protected]
aINFN,
ALICE will study nucleus-nucleus collisions at the LHC in order to investigate the properties
of QCD matter at extreme energy densities[1,2]. The measurement of open charm and open beauty
production allows to investigate the mechanisms of heavy-quark propagation, energy loss and
hadronization in the hot and dense medium formed in high-energy nucleus-nucleus collisions. In
particular, in-medium energy loss is predicted to be different for massless partons (light quarks and
gluons) and heavy quarks at moderate momentum (see e.g. [3]). The open charm and open beauty
cross sections are also needed as a reference to measure the effect of the transition to a deconfined
phase on the production of quarkonia.
The ALICE experiment is expected to provide measurements of open heavy-flavour particles in
several decay channels and with a wide phase-space coverage [2]: fully-reconstructed charm
hadronic decays at central rapidity, beauty semi-electronic decays at central rapidity, beauty
semi-muonic decays at forward rapidity. Further methods are presently under study: b-tagging of
jets, partial reconstruction of beauty decay vertices, beauty production via secondary J/ψ particles.
We shall present the latest results on the ALICE performance for production and quenching
measurements of charm and beauty particles.
References:
57
[1] ALICE Collaboration, Physics Performance Report Vol. I, J. Phys. G, V30, p.1517, 2003, and CERN/LHCC
2003-049.
[2] ALICE Collaboration, Physics Performance Report Vol. II, CERN/LHCC 2005-030.
[3] Yu.L. Dokshitzer and D.E. Kharzeev, Phys. Lett. B, v. 519, p. 199, 2001.
109
STRANGE PARTICLE PRODUCTION AND THEIR CORRELATIONS IN DIS AT HERA
B. B. Levchenko for the ZEUS Collaboration
Skobeltsyn Institute of Nuclear Physics, Moscow State University
119992 Moscow, Russian Federation, [email protected]
The production of particles with open and hidden strangeness, K0s, K±, Φ, was studied in deep
inelastic ep scattering (DIS) with the ZEUS detector at HERA. The data sample consist of DIS
events at a centre-mass-energy of 300-318 GeV and Q2 > 1 GeV2, and correspond to 120 pb-1
integrated luminosity. In the talk will be presented results on studies of kaon inclusive spectra,
Bose-Einstein correlations in one and two dimensions between identical (neural and charged) kaon
pairs, K0sK0s resonances and search for glueballs, production of a narrow baryonic state
(pentaquark)decaying to K0s-(anti)proton,direct evidence for the strange sea in the proton at low x.
110
Quarkonium Production in Heavy-Ion Collisions
with CMS Experiment at the LHC
Marc Bedjidian for the CMS Collaboration
Lyon ,Lyon, France, E-mail [email protected]
The measurement of the charmonium (J/ψ, ψ’) and bottomonium (γ, γ’, γ’’) resonances in
nucleus-nucleus collisions provides crucial information on high-density QCD matter. First, the
suppression of quarkonia production is generally agreed to be one of the most direct probes of
quark-gluon plasma formation. The observation of anomalous J/ψ suppression at the CERN-SPS
and at RHIC is well established but the clarification of some important remaining questions (role of
hadronic absorption, feed-down contributions, and extra production via recombination) requires
equivalent studies of the Υ family, only possible at the LHC energies. Second, the production of
heavy-quarks proceeds mainly via gluon-gluon fusion processes and, as such, is sensitive to
saturation of the gluon density at low-x in the nucleus (“Color Glass Condensate”). Measured
departures from the expected “vacuum” quarkonia cross-sections in Pb+Pb collisions at LHC will
thus provide valuable information not only on the thermodynamical state of the produced partonic
medium, but also on the initial-state modifications of the nuclear parton distribution functions.
We report the capabilities of the CMS detector to study quarkonia production through the dimuon
decay channel. The CMS muon acceptance is very large in the central region, |η| < 2.4, and, thanks
to the powerful tracking system and the 4 Tesla magnetic field, the dimuon mass resolution is about
54 (90) MeV at the Υ mass as measured in the barrel (barrel+endcap), the best of all LHC
experiments. Using full simulations with the most recent cross-sections estimates of the signal
(quarkonia) and backgrounds (heavy-flavour and light mesons), we present the reconstructed mass
spectra, signal/background ratios, and the expected statistics for the J/ψ and the γ family.
111
First results on J/ψ production in p-A collisions at 158 AGeV
P. Cortese a for the NA60 Collaboration
degli Studi del Piemonte Orientale and INFN, Via Bellini 25/G
I-15100 Alessandria, Italy, [email protected]
aUniversitá
The study of J/ψ production in p-A collisions is important for the understanding of the
interaction of a cc bound state in nuclear matter. Furthermore, a precise knowledge of the J/ψ
absorption cross section in nuclear matter is crucial in order to obtain an accurate baseline for the
observation of anomalous suppression effects in A-A collisions.
At the SPS, such a baseline has been obtained using a 400/450 GeV proton beam. However,
nucleus-nucleus data have been taken at considerably lower energies, 158/200 GeV/nucleon.
58
Therefore, extrapolations were needed in order to estimate nuclear absorption effects on the A-A
data samples.
For the first time at the SPS, NA60 has taken p-A data at 158 GeV, the same energy of Pb-Pb
and In-In collisions. Therefore, this set of p-A data allows a more precise and unbiased evaluation
of the normal nuclear absorption affecting J/ψ production in nucleus-nucleus interactions. In this
talk, first results on the nuclear absorption cross section σJ/ψabs for J/ψ produced by 158 GeV proton
collisions on 7 different nuclear targets (Be, Al, Cu, In, W, Pb, U) will be shown. These results will
be compared with the ones previously obtained at higher energies at SPS and RHIC. Finally, the
impact of this new measurement on the current understanding of anomalous J/ψ suppression at the
SPS will be discussed.
112
NA60 results on J/ψ suppression in In-In collisions at 158 AGeV
aINFN
E. Scomparin a for the NA60 Collaboration
- Torino, Via P. Giuria 1 I-10125 Torino, Italy, [email protected]
The suppression of J/ψ in heavy-ion collisions has been proposed long time ago as a signature
of deconfinement and is now under experimental study at SPS and RHIC energies. At the SPS, the
NA50 experiment has found that in Pb-Pb collisions the J/ψ is suppressed beyond the expectations
from nuclear absorption (anomalous J/ψ suppression). More recently, the NA60 experiment has
performed a study of muon pair production in In-In and p-A collisions, with an experimental set-up
that couples a muon spectrometer to a high-granularity vertex detector. With respect to previous
SPS experiments, NA60 has performed a dilepton measurement with a very good mass resolution
and a significant rejection of the various background sources.
By studying J/ψ production, NA60 aims at clarifying the origin of the anomalous suppression
by comparing the suppression patterns obtained with different nuclear systems as a function of
various centrality variables. In this talk, final results on the J/ψ suppression pattern obtained in In-In
collisions will be shown. In addition, results on the J/ψ transverse momentum distributions will be
presented. A comparison of the pT broadening observed at SPS and RHIC energies is indeed helpful
in order to assess the importance of recombination effects that may influence the observed J/ψ yield.
Finally, the production of a deconfined state has been predicted to influence the polarization of the
produced J/ψ. Results on the angular distributions as a function of centrality, xF and pT will be
shown.
113
Heavy Quark measurements with the Forward Silicon Vertex Tracker
David M. Lee
Los Alamos National Laboratory, for the PHENIX Collaboaration
We are designing two Forward Silicon Vertex Trackers (FVTX) for the PHENIX experiment at
RHIC. These trackers would extend the vertex capability of the PHENIX Silicon Vertex Tracker
(VTX) to forward and backward rapidities with secondary vertex capability in front of the PHENIX
muon arms. The identification of secondary vertices opens up a wide variety of improvements in the
understanding of important physics processes. In heavy quark (charm and beauty) production, the
lifetime of the heavy meson (combined with a significant boost at RHIC energies) allows travel of a
few millimeters before decaying into a lepton and/or other products. For example, this permits
explicit identification of beauty production through the channel B  J/ψ X and event by event
tagging of the semileptonic decays D and B  X. Also, numerous pions and kaons decay into
muons and other products in the first few centimeters of their travel, and the event-by-event
identification and rejection of this voluminous source of secondary muons will reduce the level of
background in a variety of physics channels. Combining secondary vertex identification with the
existing muon spectrometers provides a powerful improvement in the capabilities of the muon
detector system and extends our physics reach in the large rapidity () and low momentum-fraction
59
(x) regions; and (with sufficient luminosity) to high transverse momentum.
The FVTX will be composed of two endcaps, with four silicon mini-strip planes each, covering
angles (10 to 35 degrees) to match the two muon arms. Each silicon plane consists of wedges of
mini-strips with 75 μm pitch in the radial direction and lengths in the phi direction varying from 1.9
mm at small angles to 13.5 mm at 35 degrees. A resolution in zvertex of 200 μm can be achieved with
a maximum occupancy per strip in central Au-Au collisions of less than 2.7%. We will use a new
data push technology for the readout electronics that will allow for a fast triggering capability.
This talk will summarize the physics capability of the FVTX, the technology choices, and test results.
114
The Centrality Dependence of Strange Baryon and Meson Production in Cu+Cu and Au+Au
Relativistic Heavy Ion Collisions with s NN = 200 GeV
Anthony Timminsa for the STAR Collaboration
of Physics and Astronomy, University of Birmingham, Edgbaston,
Birmingham, B15 2TT, United Kingdom, [email protected]
aSchool
Results from RHIC on the centrality dependence of strange particle production in Au+Au have
shown that several measured quantities at mid-rapidity increase quite rapidly in the region where
the number of participants, Npart, is less than ~100-150. Examples include the enhancement of
strange baryons, from measuring total yields per participant relative to p+p collisions, and the
strangeness suppression factor γs derived from thermal models. When strange baryon and meson
yields are investigated as a function of transverse momentum, pT, and scaled by the number of
binary collisions, suppression is observed at high pT in central relative to peripheral collisions. In
this case, the suppression sets in for strange mesons at lower pT than for strange baryons. These
observations provide a powerful insight into the interplay between the partonic energy loss, and the
recombination of thermal strange and nonstrange quarks.
Data taken from Cu+Cu s NN = 200 GeV collisions at the STAR experiment offer enhanced
statistics with a better defined collision geometry for this collision energy and system size regime.
These data are used to show in detail the evolution of enhancement factors and γs as function of
Npart. The pT dependence of binary scaled strange baryons and mesons yields for different
centralities are also measured. These are used to examine ratios of such yields for central to
peripheral Cu+Cu collisions, and for central Au+Au collisions to central Cu+Cu collisions in order
to extract more quantitative high pT suppression factors.
115
Xiao-Ming Zhang
Institute of Particle Physics, Huazhong Normal University
Wuhan, Hubei, 430079, P. R. China, [email protected]
Radiative energy loss rate of heavy quark traversing through thermal dense matter which is
formed in heavy ion collisions has been studied under an assumption of valid factorized method , in
which light quark radiative spectrum is used to multiply an dead-cone factor depending on quark
mass and energy. The calculated numerical results with energies at RHIC and LHC show that the
heavy quark radiation spectra, obtained by extending light quark energy spectrum, are
approximately consistent with the result under pQCD frame by Djordjecvic-Guulassy. The
calculation is simplified by using factorial dead cone factor and the equivalent results can be got.
References:
[1] Y.L. Dokshitzer, DE. Kharzeev, phys.Lett.B, 519(2001)100.
[2] M. Djordjevic, M. Gyulassy, Phys.Rev. C, 68 (2003) 034914.
[3] N. Armesto, C A. Salgaldo, and U A. Wiedemann, Phys. Rev. D.,69, 114003(2004)1-16.
[4] Nestor Armesto, Carlos A. Salgado,and Urs Achim Wiedemann Phys.Rev., D69 (2004) 114003.
[5]R. Thomas,B. Kampfer,and G. Soff Acta Phys.Hung,A22 (2005) 83-91 .
116
60
High pT azimuthal and pseudorapidity correlations with strange baryons
and mesons at RHIC
J. Bielcikovaa for the STAR Collaboration
Physics Department, Yale University, New Haven, CT-06520, USA
[email protected]
a
As a direct measurement of jets in nuclear collisions is difficult due to the large multiplicities of
emitted particles, azimuthal correlations of particles with large transverse momentum pT are
commonly used to study jet-related processes. Identified two-particle correlations are expected to
provide additional information on anomalous baryon production, long-range pseudorapidity
correlations and particle production mechanisms at RHIC energies.
The wealth of data collected by the STAR experiment in p+p, d+Au, Cu+Cu and Au+Au
collisions at s NN = 200 GeV offers the possibility of investigating in detail azimuthal and
pseudorapidity correlations of strange mesons (KS0) and strange and multiply-strange baryons (λ,
λbar, Ξ and Ω) for pT=2-6GeV/c. The study is performed for both identified strange trigger particles
associated with charged particles as well as charged trigger particles using identified associated
strange particles.
We study the yield of associated particles as a function of centrality of the collision,
pseudorapidity and transverse momentum of trigger and associated particles to look for possible
flavor, baryon/meson and particle/antiparticle differences. We compare our results to the
correlations using identified protons and pions as well as to fragmentation and recombination
models. Especially, the study of correlations using multiply-strange trigger particles is a critical test
of the validity of the recombination picture. In particular, the Ω-triggered correlations are expected
to be swamped by the background up to pT = ~8GeV/c [1] and should not be observable.
References:
[1] R.C. Hwa, C.B. Yang, nucl-th/0602024.
117
STATISTICAL HADRONIZATION OF HEAVY QUARKS IN NUCLEUS-NUCLEUS
COLLISIONS
A. Andronica, P. Braun-Munzingera,b, K. Redlichc, J. Stacheld
für Schwerionenforschung, GSI, D-64291 Darmstadt, Germany
c Institute of Theoretical Physics, University of Wroclaw, PL-50204 Wroclaw, Poland
d Physikalisches Institut der Universität Heidelberg, D-69120 Heidelberg, Germany
a Gesellschaft
We present new results of the statistical hadronization model [1] for heavy quarks at RHIC and
LHC energies, in particular on the phase space (rapidity and transverse momentum) distributions.
Several new aspects are considered within the model, together with a critical assessment of their
in°uence on the results. At RHIC we investigate the centrality dependence of the J/ψ production
focusing on the model results for different values of the charm cross section, including its
theoretical and experimental uncertainty. For the ¯rst time we investigate within this model the
rapidity dependence of the J/ψ yield, which reproduces very well recent data available at RHIC
from the PHENIX experiment [2]. At LHC energy, we update our model predictions for the
centrality dependence of J/ψ yield and investigate as well the rapidity dependence. We discuss the
transverse momentum distribution of J/ψ expected from the model and provide predictions for a
range of values of the expansion velocity at chemical freeze-out. We extend the model for the
calculation of ¨ yields in Pb+Pb collisions at LHC energy.
References:
[1] P. Braun-Munzinger, J. Stachel, Phys. Lett. B 490 (2000) 196,A. Andronic et al., Phys. Lett. B 571 (2003) 36.
[2] H. Pereira Da Costa (PHENIX), nucl-ex/0510051.
118
Thermalization of Heavy Quarks and Consequences
on Non-photonic e- p┴ Spectra
61
Vincent GUIHOa
Laboratory, Ecole des Mines de Nantes, 4 rue Alfred Kastler, BP 20722, 44307 Nantes
cedex 3, France, [email protected]
a SUBATECH
Thermalization of heavy quarks in QGP has been investigated in Fokker-Planck formalism. A
hydrodynamical model which simulates the evolution of non-central heavy ion collisions has been
used, and we have also take into account recombinations of charm quarks in J/ψ. Extending our
previous studies[1], radiative transport coefficients of the Fokker-Planck equation are calculated
within perturbative QCD. We find an important growth of radiative coefficients with energy in
opposition to collisional case, and we show that diffusion coefficient plays a non-negligible role in
phase distribution of heavy quarks, which influence J/ψ's formation pattern. Nuclear modification
factors and v2 of leptons from D mesons decay are evaluated. First one is found to be in good
agreement with recents Phenix experiment measurements[2] for all centralities, but second one not.
There is two phenomena in competition here : energy loss and spatial distribution in function of
time. The more a heavy quark loses energy and momentum (RAA decreases), the more it will spend
time to lose it, and since in the hydrodynamic model light quarks have their higher v2 value just after
the QGP formation, if a heavy quark go out of plasma at these early time of the collision (small
energy loss, far from thermalization), it will hadronize with large-elliptic-flow-light-quarks and D
mesons will have a large v2, whereas if a heavy quark go out of plasma after a long time (large
energy loss, close to thermalization), it will hadronize with low-elliptic-flow-light-quarks. Thus, as
opposed to what one thinks, it is completely normal, in the frame of our model, that a large RAA is
synonymous with a small v2. It could be revealed that largeness of leptons v2 comes from hadonical
phase by a majority.
References:
[1] V. Guiho, P.B. Gossiaux and J.Aichelin, J.Phys. G31 (2005) S1079-S1082, ep-ph/0411324
[2] Phenix collaboration, Phys.Rev.Lett. 96, (2006) 032001
119
J/ψ PRODUCTION FROM CHARM COALESCENCE IN RELATIVISTIC
HEAVY ION COLLISIONS
Bin Zhang
Department of Chemistry and Physics, Arkansas State University, P.O. Box 419, State University, AR
72467-0419, USA, [email protected]
In relativistic heavy ion collisions, J/ψ production is closely related to the production of the
strongly interacting Quark-Gluon Plasma (sQGP). To study the effects of charm quark dynamics on
J/ψ production, the phase space distributions of charm and anti-charm quarks are generated using A
Multi-Phase Transport (AMPT) model. These charm quarks then coalesce into J/ψ particles. The
production and flow of J/ψ show strong sensitivity to final state charm interactions. The results are
compared to charm quark and D meson results from the AMPT model and recent predictions from
other models. A discussion will be given with the implications of this study on the properties of the
sQGP.
References:
[1] B. Zhang, "J/ψ production from charm coalescence in relativistic heavy ion collisions,"
arXiv:nucl-th/0606039.
120
J/ψ production relative to the reaction plane in Pb-Pb collisions
at the CERN SPS
a
F. Prinoa for the NA50 collaboration
INFN, Sezione di Torino,Via P. Giuria 1, 10125, Torino, Italy,[email protected]
We present the results of a measurement of J/ψ production in Pb-Pb collisions at 158
GeV/nucleon as a function of the J/ψazimuthal angle relative to the reaction plane. Although charm
thermalization is not likely to occur at SPS energies, some physical mechanisms related to
charmonium absorption in the medium formed in the collisions are expected to introduce an
anisotropy in the azimuthal distribution of the measured J/ψ mesons. The analysis has been
62
performed on a data sample of about 100000 J/ψ events, collected in year 2000 by the NA50
Collaboration, under optimized experimental conditions. The reaction plane was estimated from the
azimuthal distribution of the neutral transverse energy in an electromagnetic calorimeter.
We present the measured distributions of J/ψ azimuthal angle relative to the reaction plane, as
well as the extracted Fourier coefficients v1 and v2 as a function of the collision centrality and of the
J/ψ transverse momentum.
121
Heavy flavor production in pA collisions within the MV+BK framework
H. Fujiia, F. Gelisb and R. Venugopalanc
Institute of Physics, University of Tokyo Komaba, 153-8902, Japan [email protected]
b
Service de Physique Théorique, Bát. 774, CEA/DSM/Saclay
91191 Gif-sur-Yvette Cedex, France, [email protected]
c
Physics Department, BNL, Upton, NY 11973, USA, [email protected]
a
We present a calculation for the heavy quark production in high energy proton-nucleus (pA)
collisions in the Color Glass Condensate (CGC) approach, which treats consistently both multiple
scattering and small x quantum evolution. The nuclear correlation functions appearing in the
production cross section[1], are evaluated first in the McLerran-Venugopalan model[2] and then
evolved to lower x values by the Balitsky-Kovchegov equation[3]. This calculation is important as a
base-line study of the the heavy flavor yields in high-energy nucleus-nucleus collisions at RHIC and
LHC, where dense partonic initial condition becomes very relevant. First we present general
features of the pair productions. The logarithms seen in our numerical results are related to those
appear in the collinear factorization in QCD, and the violation effect of k┴ factorization is
re-investigated under both the effects of the x-evolution and the multiple scattering[2]. Solving the
x-evolution numerically, we provide results for the rapidity distribution of the pairs and the
behavior of the nuclear R ratios.
Next we will discuss the result of the heavy meson production in the pA reactions. For the open
heavy flavors (charm and bottom), we will convolute the quark production cross section with a
fragmentation function to obtain the observed meson spectrum. We also compute the hidden heavy
flavor states, quarkonium (J/ψ and γ), by utilizing the color evaporation model[3].
References:
[1] J.P. Blaizot, F. Gelis and R. Venugopalan, Nucl. Phys. A 743, 13 (2004); Nucl. Phys. A 743, 57 (2004).
[2] H. Fujii, F. Gelis, and R. Venugopalan, Phys. Rev. Lett. v. 95, p. 162002, 2005.
[3] H. Fujii, F. Gelis, and R. Venugopalan, hep-ph/0603099; in preparation.
122
Charm Quark Energy Loss in Dense Matter within the Light-Cone
Path Integral Approach
Yaxian Mao
Institute of Particle Physics, Central China Normal University
Wuhan, Hubei, 430079, P. R. China,[email protected]
The energy loss of charm quark in a _nite size of quark-gluon plasma is studied within the
light-cone path integral approach. A simple analytical formulation of the radiative energy loss of
charm quark is derived. This provides a convenient way to quantitatively estimate the heavy quark
energy loss. Our results show that the quark energy loss obviously depends on the mass of quark, i.e.
a remarkable suppression occurs in the case of heavy quark comparing to the light one. And if the
energy of the heavy quark is much larger than its mass, the radiative energy loss of heavy quark
approaches to the radiative energy loss of light quark.
References:
[1]A. Adil, M. Gyulassy, W. A. Horowitz, S. Wicks, Collisional Energy Loss of Non Asymptotic
Jets in a QGP. nucl-th/0606010
[2]M. G. Mustafa, Energy Loss of Charm Quarks in the Quark-Gluon Plasma: Collisional
[3]B. G. Zakharov, Radiative parton energy loss and jet quenching in high-energy heavy-ion
63
collisions, JETP. Lett., 2004,80:617D622.
[4]M.Gyulassy,P.Levai, I. Vitev, Non-abelian energy loss at _nite opacity, Phys. Rev. Lett.,
2000, 85: 5535D5538.
[5]R. Baier, Y. L. Dokshitzer, et al., Medium-induced radiative energy loss; equivalence
between the BDMPS and Zakharov formalisms, Nucl. Phys., 1998, B531: 403D425.
[6]B. G. Zakharov, Fully quantum treatment of the LandauDPomeranchukDMigdal e_ect
in QED and QCD, JETP Lett., 1996, 63: 952D957.
[7]M. Gyulassy, X. N. Wang, Multiple collisions and induced gluon bremsstrahlung in QCD.
Nucl. Phys, 1994, B420: 583D614.
123
HEAVY QUARK ENERGY LOSS THROUGH SOFT QCD
SCATTERING IN THE QGP
K. Zapp a, G. Ingelman b and J. Stachel a
Physikalisches Institut, Universität Heidelberg
Philosophenweg 12, D-69120 Heidelberg, Germany, [email protected]
b High Energy Physics, Uppsala University, Box 535, S-75121 Uppsala, Sweden
a
The apparent strong suppression of heavy quarks in Au+Au collisions at Rhic at high
transverse momenta, as reflected in the non-photonic electron spectrum, seems to indicate that
collisional energy loss plays an important role for the energy loss of energetic quarks. We
investigate the energy loss of heavy quarks in the framework of the SCI Jet Quenching model [1],
which is a model for energy loss through soft QCD scatterings in the quark-gluon plasma. Once the
parameters are fixed for light quarks it can be applied to heavy flavours without changes.
The heavy quark spectra needed as input are generated with Pythia (i.e. with leading order massive
matrix elements). The parton shower evolution, fragmentation and decays are also simulated with
PYTHIA; for the interactions with the QGP the SCI Jet Quenching model is used. For electrons from
charm decays we find a suppression which is similar to the result for π0. The suppression of
electrons from beauty decays, on the other hand, is smaller. Since beauty dominates the electron
spectrum at moderate and high p the overall suppression of non-photonic electrons is smaller than
indicated by preliminary Phenix and Star data. The number of scatterings is the same for light and
heavy quarks, but the energy loss per scattering is smaller for heavy flavours due to kinematics (a
heavy object takes less recoil). This explains the stronger suppression of charm as compared to
beauty.
The fact that the suppression of electrons from charm decays is comparable to the π0
suppression has to be regarded as a coincidence: The slope of the charm quark spectrum is very
similar to the spectrum of light quarks and gluons (which are the dominant sources of π0) over many
orders of magnitude. But electrons at a given p stem from harder quarks (charm or beauty) then
pions with the same p . This effect partly compensates the smaller energy loss of heavy quarks. As
a consequence one would also expect a weaker dependence on centrality of the electron RAuAu.
These considerations are mostly model independent, only the exact magnitude of the energy loss is
specific for our model.
⊥
⊥
⊥
References:
[1] K. Zapp, G. Ingelman, J. Rathsman and J. Stachel, Phys. Lett. B 637 (2006) 179 [arXiv:hep-ph/0512300].
124
Heavy Quark Diffusion in N=4 Yang-Mills at Strong Coupling
J. Casalderrey-Solana a and D. Teaney b
Nuclear Science Division, Lawrence Berkeley National Laboratory
Berkeley, CA, 947, USA, [email protected]
b Department of Chemistry and Physics, PO Box 419
Arkansas State University, AR, 72467, USA, [email protected]
a
We express the heavy quark diffusion coefficient as the temporal variation of a Wilson line
along the Schwinger-Keldysh contour. This generalizes the classical formula for diffusion as a
force-force correlator to a non-abelian theory. We use this formula to compute the diffusion
64
coefficient in strongly coupled N=4 Yang-Mills by studying the fluctuations of a string in AdS5×S5.
The string solution spans the full Kruskal plane and gives access to contour correlations. The
diffusion coefficient is D  2 / T and is therefore parametrically smaller than momentum
diffusion,  /( e  p)  1 / 4T . The quark mass must be much greater than T /  in order to treat
the quark as a heavy quasi-particle. The result is discussed in the context of the RHIC experiments.
125
Charm-anticharm azimuthal correlations at RHIC
Denes Molnar Purdue University, U.S.A.
An exciting puzzle at RHIC is the surprisingly strong suppression of heavy(c, b) quarks, as
suggested by non-photonic single electron measurements. Additional insights could be gained from
electron elliptic flow data, however, statistics so far has been poor. In this talk I will present
predictions from covariant transport theory on a novel observable - charm-anticharm azimuthal
correlations. The azimuthal correlation pattern gives an independent "measure" of the opacity that
provides a cross-check for values extracted from the nuclear suppression and elliptic flow. Results
for hidden charm (J/ψ) production, which is yet another "orthogonal" observable, will also be
discussed.
126
Heavy Quarkonium Survival in Quark-Gluon Plasma
RIKEN-BNL Research Center, Brookhaven National Laboratory
Upton, NY, 11973, USA, [email protected]
I review our current theoretical understanding of the disappearance of heavy quarkonium states
at high temperatures in a quark-gluon-plasma. Special attention is given to potential models
utilizing a variety of potentials and their comparison to lattice QCD results. Even though certain
potentials yield dissociation temperatures in accord with lattice results, there are unreconciled
differences when comparisons are made directly to correlators and to the spectral functions. I also
show that one could obtain qualitative agreement with lattice calculations using specially
constructed screened Cornell potential. This screening, however, does not correspond to
Debye-screening. Finally, I discuss recent developments in our understanding of different quarkonia
dissociation mechanisms and specify how experiments might distinguish between these scenarios.
127
Study B and D Contributions via Azimuthal Correlations between
Xiaoyan Lin (for the STAR Collaboration)
Institute of Particle Physics, Wuhan, 430079, P. R. China
University of California, Los Angeles, CA 90095,USA
The suppression of high-pT hadron yields and correlations measured in central Au+Au
collisions at RHIC presents strong evidence for significant final state parton energy loss in the
produced strongly interacting medium. Recently, the STAR collaboration has measured a similarly
strong suppression for non-photonic electrons in a pT range where they are expected to be
dominated by semi-leptonic charm and bottom decays. This observation challenges theoretical
predictions of energy loss for heavy quarks.
Azimuthal correlations of non-photonic electrons and charged hadrons will yield essential
information on heavy flavor production and may allow discrimination between charm and bottom
due to different decay kinematics and away side particle (or jet) composition.
In this talk, we will present preliminary measurements of azimuthal correlations between
high-pT non-photonic electrons and charged hadrons in elementary p+p and d+Au collisions at 200
GeV. Preliminary results on the relative contribution of D and B mesons to the non-photonic
electrons are presented. These measurements will provide reference data for similar measurements
65
in heavy-ion collisions, which will allow for the study of heavy quark energy loss in more detail.
128
 Production at RHIC: Characterization of Coexistence Phase
J. K. Nayaka,J. Alama B. Mohantya,P. Royb and A.K. Dutt-Mazumderb
aVariable Energy Cyclotron Centre, 1/AF, Bidhan Nagar Kolkata 700 064, India.
b Saha Institute of Nuclear Physics, Physics, 1/AF, Bidhan Nagar Kolkata 700 064, India
The production of strangeness in ultra-relativistic heavy ion collisions has been considered.
Assuming a first order phase transition, the evolution of strange particles have been studied by
using Boltzmann equation. The results obtained have been contrasted with the experimental data of
the RHIC experiment presented by the STAR collaboration. Data on  at mid rapidity for Au+Au
collision at s =200 GeV is used to set a lower bound to the critical temperature of quark hadron
phase transition. The effective degrees of freedom that characterizes the co-existing phase of quark
gluon plasma and hadrons has also been extracted.
129
K*(892) production in Au-Au collisions at RHIC
Xin Dong for the STAR Collaboration
Department of Modern Physics, University of Science and Technology of China
Hefei, Anhui 230026, P.R. China
Short-lived resonances are useful tools to probe the property of the matter created in heavy ion
collisions. Measurements of their production yields and elliptic flow allow us to understand
particle production mechanisms as well as the system evolution after hadronization. We report the
measurements of transverse momentum spectrum and the elliptic flow of K * resonance up to
intermediate pT region in mid-rapidity through its hadronic decay channel using the STAR detector
in Au-Au collisions at √sN N = 200 GeV. Its nuclear modification factor as well as elliptic flow will
be compared with those results of Ks and Lambda up to intermediate pT to check the number of
quark scaling for resonances. Combining the K * /K yield ratio and the scaling check for K * , the
production mechanism of K * will be discussed The first results on K * pT spectra from Au+Au
62.4 GeV will presented to understand the energy dependence of K * production.
130
Search for Exotic Multi-quark Resonances in Relativistic Nuclear Collisions
Fan. Wang
Dept of Physics, Nanjing Univ, China, [email protected]
QCD does not deny quark gluon exotics, such as glueball, quark-gluon hybrid, multi-quark
state, etc. Up to now no any exotic has been well established experimentallly. We will argue that if
our understanding of quark confinement obtained from lattice QCD calculations is qualitatively
correct, multi-quark resonances are unavoidable. Relativistic heavy ion collision should be a good
place to create multi-quark resonances. Experimental search for multi-quark resonnces with the
existed detectors at RHIC are proposed.
131
OPEN CHARM RECONSTRUCTION IN ALICE: D+ → K −π+π+
aUniversity
E. Brunaa (for the ALICE Collaboration)
of Torino, Via P. Giuria 1, 10125 Torino, Italy, [email protected]
Open charmed
mesons produced in high energy A-A interactions are expected to be powerful
s
probes to investigate the medium produced in the collision. In this context it is important to measure
as many charmed hadrons as possible, such as D0, D+ and Ds+, because the measurement of their
relative yield can provide information on the hadronization mechanism and is necessary to reduce
the systematic error on the absolute cross section. The ALICE experiment at the LHC is designed to
perform such measurements at midrapidity down to pT∼1 GeV/c, mainly by means of the silicon
66
vertex and tracker detector, the time projection chamber and the time of flight detector.
One of the currently ongoing studies related to the detection of heavy-flavour particles in
ALICE is the exclusive reconstruction of the D+ meson through its three charged body decay K
− + +
π π in Pb-Pb (√s = 5.5 TeV) and p-p (√s = 14 TeV) collisions. The selection strategies for this
analysis and the results of a feasibility study on Monte Carlo events will be presented together with
the perspectives for D+ quenching and azimuthal anisotropy measurements.
132
Non-photonic electron yields from Cu+Cu collisions at
$\sqrt{s_{NN}} = 200$ GeV at STAR.
Anders Knospe (for the STAR Collaboration)
Yale University
All partons are thought to lose energy through gluon radiation as they pass through the hot and
dense medium produced in high-energy nucleus-nucleus collisions. It is expected that heavy quarks
lose less energy in the medium than light quarks due to the suppression of small-angle gluon
radiation (the dead cone effect). Thus, heavy quarks should be a sensitive probe of the medium.
Heavy-quark production can be measured through the spectrum of non-photonic electrons, which is
dominated by the semileptonic decays of heavy-flavor mesons.
Preliminary non-photonic electron spectra are extracted for Cu+Cu collisions at $\sqrt{s_{NN}} = 200$ GeV and are compared to the non-photonic electron yields from p+p and Au+Au collisions
at the same energy. This provides a valuable test of the dependence of the non-photonic electron
yield on system size.
133
Centrality dependence of J/ψ production in Au+Au and Cu+Cu collisions by the
PHENIX Experiment at RHIC
T. Gunjia for the PHENIX Collaboration
for Nuclear Study, University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
[email protected]
aCenter
Experimental studies at the Relativistic Heavy Ion Collider (RHIC) have been performed to find
and study a plasma state of deconfined quarks and gluons, called the quark-gluon-plasma (QGP).
The J/ψ has long been considered as one of the most promising probes to study the formation of
the QGP, since the J/ψ yield was expected to be suppressed due to color Debye screening in the
QGP. Recent numerical lattice QCD calculations however indicate that the J/ψ will survive as a
bound state at RHIC energies, while χc and ψ’ will be dissolved around the critical temperature Tc.
Since about 40% of J/ψ come from the feed down of χc and ψ’, this will result in a reduction of the
J/ψ yield even if the direct J/ψ’s are not suppressed themselves. Several models predict that the J/ψ
yield will be a balance between destruction due to gluon rescattering and enhancement due to the
recombination of uncorrelated c c pairs, which are produced abundantly in the initial collisions at
RHIC energy.
To understand the J/ψ production in hot and dense matter and differentiate between these
competing effects, it is important to do systematic studies of J/ψ production with several system
sizes and collision energies. PHENIX has measured the J/ψ yield in Au+Au and Cu+Cu collisions
at sNN =200GeV at both mid-rapidity and forward-rapidity. The latest results of the centrality
dependence of the nuclear modification factor RAA for the J/ψ in Au+Au and Cu+Cu collisions
will be shown and compared to the theoretical models to extract the in-medium effects on the J/ψ
production.
134
Measurement of leptonic and hadronic decays of ω and φ mesons at RHIC by PHENIX
aHEPD,
Yu. Riabova for the PHENIX collaboration
Petersburg Nuclear Physics Institute Gatchina, Russia, [email protected]
67
Properties of short lived mesons such as ρ, ω and φ produced in heavy ion collisions have been
a subject of special interest among physicists. It is believed that masses, widths and branching ratios
of these particles may change near the phase transition into the newly discovered state of matter, the
Strongly-coupled Quark-Gluon Plasma (sQGP) observed in relativistic heavy ion collisions. The
detailed study of such modifications is a way to investigate the properties of the sQGP observed at
RHIC. Due to its precise tracking and calorimetry systems, excellent electron identification and
flexible trigger the PHENIX experiment possesses unique capabilities to simultaneously measure
both the leptonic and various hadronic decay modes of the particles produced in the collisions. That
allows to perform the most comprehensive study of the ω and φ meson production in different
collisions systems at RHIC. In this talk we present the latest results on the ω and φ meson
production measured at midrapidity in di-electron and several hadronic decay channels in p+p,
d+Au, Cu+Cu and Au + Au collisions at the highest RHIC energy. The results are compared
between different decay modes and to the results of the other particle production measurements at
the same and at lower energies.
135
Scaling of charm integrated cross section and modification of its transverse momentum
spectra in d+Au and Au+Au collisions at RHIC
C. Zhonga for the STAR Collaboration
of Nuclear Physics, Shanghai Institute of Applied Physics
Shanghai 201800, P. R. China, [email protected]
In relativistic heavy-ion collisions, charm quarks are believed to be produced at early stages via
initial gluon fusion and their production cross section can be evaluated by perturbative QCD [1].
Study of the binary collision (Nbin) scaling properties for the charm total cross section among p+p,
d+Au to Au+Au collisions can test if heavy-flavor quarks are produced exclusively at initial impact
[2]. Due to the heavy mass of charm quark, charmed hadrons might freeze out earlier than light
flavor hadrons. Their flow velocity might be a good indicator of light flavor thermalization
occurring at the partonic level [3, 4, 5]. Charm energy loss, highly sensitive to the properties of
medium, can be inferred by the modification factor of its semileptonic decayed electron.
Besides the measurement of D meson production from the analysis of their hadronic (D0 ->K
up to 3 GeV/c) and semileptonic (D -> e+X at 0.9<pT<5.0 GeV/c) decays in sNN =200 GeV
Au+Au collisions, we proposed and measured D ->μ+X at 0.17<pT<0.27 GeV/c, which greatly
constrains the charm total cross section [2]. In addition, we are able to extract freeze-out parameters
based on a blast-wave model. The transverse momentum (pT ) spectra and the nuclear modification
factors for D0 and for electron/muon from charm semileptonic decays will be presented. The
differential cross-section d/dy of charm production at sNN = 200 GeV in d+Au and Au+Au
collisions will be reported.
References
[1] M. Cacciari, P. Nason and R. Vogt, Phys. Rev. Lett. 95, 2005 (122001)
[2] H.D. Liu et al., Phys. Lett. B 639, 2006 (441-446) e-print Arxiv: nucl-ex/0601030
[3] STAR Collaboration, J. Adams et al., Phys. Rev. Lett. 92, 112301 (2004)
[4] B. Zhang et al., nucl-th/0502056
[5] S. Batsouli et al., Phys. Lett. B 557, 2003 (26-32) e-print Arxiv: nucl-th/0212068
136
Heavy Quarkonia Production in p+p collisions from the PHENIX Experiment
Abigail Bickley for the PHENIX Collaboration
Department of Physics, 390 UCB
Quarkonia provide a sensitive probe of the properties of the hot dense medium created in high
energy heavy ion collisions. Hard scattering processes result in the production of heavy quark pairs
that interact with the collision medium during hadronization. These in-medium interactions convey
information about the fundamental properties of the medium itself and can be used to examine the
68
modification of the QCD confining potential in the collision environment. Baseline measurements
from p+p and d+Au collision systems are used to distinguish cold nuclear matter effects while
measurements from heavy ion collision systems are used to quantify in-medium effects. The
PHENIX experiment has the capability of detecting heavy quarkonia at forward rapidity (1.2 < |η|
< 2.2) via the µ+µ− decay channel and at mid-rapidity (|η| < 0.35) via the e+e− decay channel.
Recent runs have resulted in the collection of high statistics p+p data sets that provide an essential
baseline reference for heavy ion measurements and allow for further critical evaluation of heavy
quarkonia production mechanisms. The latest PHENIX results for the production of the J/ψ, χc and
 in p+p collisions will be presented. In light of the newly available reference data, the
implications of the J/ψ results in the d+Au collision system on cold nuclear matter effects will be
revisited. Furthermore, the χc data will be examined to establish the baseline feed- down
contribution.
137
Ξ0(1530) Production in Heavy-Ion Collisions and its Implications for ∆ttherm-chem
aYale
R. Witta for the STAR Collaboration
University, New Haven, CT, 06520, U. S. A., [email protected]
Hadronic scattering in the late stages of a heavy-ion collision may modify the chemical
composition of the system up to the time of chemical freeze-out, after which all non-resonance
particle ratios are fixed. However, resonances may still be produced through inelastic hadronic
scatterings, their production rates being dependent on the relatively poorly known hadronic
cross-sections (Ξ− + π+ → Ξ∗(1530), Λ + π± → Σ∗(1385), etc.) [1-4]. Similarly, rescattering of the
daughters of primary resonances whose lifetimes are shorter than the lifetime of the colliding
system may destroy their correlations and prohibit the parent resonance reconstruction, leading to
an underestimated primary yield. The interplay of these two effects may continue from the time of
chemical freeze-out (tchem) to the time of ther- mal freeze-out (ttherm) and the degree to which the
primary resonance yields are modified depends on the length of this time interval (∆t = ttherm − tchem)
and the relative strengths of the two effects [5-9]. It has also been suggested that the in vacuo
resonance masses and widths might be modified in the presence of the nuclear medium [10].
We present the first ever measurements of the transverse momentum spectra and mid-rapidity
yields of the multi-strange baryon resonance, Ξ0(1530), and its anti-particle, from √sNN =200 GeV
Au+Au collisions from the STAR experiment at Brookhaven National Laboratory. Ratios of the
mid-rapidity yield of this long-lived (cτ = 21 fm) resonance to its non-resonance partner (the Ξ
baryon) will be compared to predictions from thermal models and to the corresponding ratios for
other resonances measured by STAR [11]. Conclusions will be drawn about the implication of these
measurements for ∆t and any observed deviation from the expected mass and width will be
discussed.
References:
[1] S.A. Bass et al., Phys. Rev. C61, 064909 (2000).
[2] R. Rapp et al., Phys. Rev. Lett. 86, 2980 (2001).
[3] H. van Hees et al., Phys. Lett. B606 59 (2005).
[4] C. Adler et al. (STAR Collaboration), Phys. Rev. C66, 061901 (2002).
[5] M. Bleicher et al., Phys. Lett. B530, 81 (2002).
[6] M. Bleicher, Nucl. Phys. A715, 85 (2003).
[7] G. Torrieri et al., Phys. Lett. B509, 239 (2001).
[8] J. Rafelski et al., Phys. Rev. C64, 054907 (2001).
[9] J. Rafelski et al., Phys. Rev. C65, 069902,(2002).
[10] M.F.M. Lutz et al., Nucl. Phys. A700, 193 (2002).
[11] J. Adams et al. (STAR Collaboration), arXiv:nucl-ex/0604019.
138
HEAVY QUARK MODIFICATION IN A COMBINED TRANSPORT + QUENCHING
APPROACH
I. Viteva, H. van Heesb
69
a
Los Alamos National Laboratory, Theoretical and Physics Divisions
Los Alamos, NM 87545 USA, [email protected]
b
Cyclotron Institute,TexasA&M University,College Station, TX 77843 USA, [email protected]
We revisit the question regarding the origin of the nuclear modification of non-photonic
electrons in Au+Au collisions at RHIC by combining for the first time radiative energy loss,
collisional energy loss and D- and B-resonance interaction calculations to evaluate the drag and
diffusion coefficients for heavy quarks in the quark-gluon plasma and the mixed phases of heavy
ion reactions. These coefficients are applied in a relativistic Fokker-Planck equation, which is
solved by an equivalent Langevin simulation to describe heavy-quark quenching and diffusion
within the quark-gluon plasma. The single electron data from STAR and PHENIX on the nuclear
suppression RAA(pT) and the elliptic flow v2(pT) measured at RHIC are compared with our
theoretical model.
References:
[1] H. van Hees, I. Vitev, in preparation.
139
PHENIX results for J/ψ transverse momentum and rapidity dependence
in Au+Au and Cu+Cu collisions
A. Glenna for the PHENIX Collaboration
[email protected]
Heavy quarkonia production is considered to be one of the most important probes of the hot
and dense state created in relativistic heavy ion collisions. At RHIC energy J/ψ yields, including the
contributions from χc and ψ0 states, are expected to be suppressed in a quark gluon plasma due to
color screening and gluon rescattering. Competing processes such as quark recombination may also
play an important role. Detailed models with different production and suppression contributions
may generate similar centrality trends while presenting distinctions in rapidity and/or transverse
momentum distributions. For example, J/ψ recombination from thermalized quarks could be
particularly evident in transverse momentum modifications. The PHENIX experiment at RHIC has
measured J/ψ production in sNN ＝200GeV Au+Au and Cu+Cu collisions at forward (1.2<|y|<2.2)
and mid (|y|<0.35) rapidities. The most recent results for the rapidity and transverse momentum
dependence of J/ψ production will be discussed and compared with PHENIX baseline p+p and
d+Au measurements and various theoretical calculations.
140
Heavy Quark Measurements by Single Electrons in the PHENIX Experiment
Fukutaro Kajihara for the PHENIX Collaboration
Center for Nuclear Study (CNS), Graduate School of Science, the University of Tokyo CNS in RIKEN,
2-1 Hirosawa, Wako, Saitama, 351-0198, Japan, [email protected]
Strong suppression of light flavor mesons at high pT has been observed in relativistic heavy ion
collisions at RHIC. The suppression is ascribed to jet quenching effects of light quarks and gluons
and reveals that very dense matter is created that is not conventional hadronic matter. Heavy quarks
(charm/bottom) provide probes of the newly created matter with important differences. Heavy
quarks are predicted to lose less energy in the medium because of their large masses, and to have
much longer thermal equilibration time constants. PHENIX has measured single (nonphotonic)
electrons in 1.0< pT <5.0GeV/c which are produced from semileptonic decays of heavy flavor
mesons in Au+Au collisions at sNN = 200GeV and reported very large suppression, similar to that
for light mesons. This talk will show the latest results of single electron measurements in PHENIX
which covers lower and higher pT region. Especially, the new result in pT > 5.0GeV/c is important
to understand unknown bottom quark behavior in the very dense matter.
141
70
A d+Au data-driven prediction of cold nuclear matter effects on J/ψ production in Au+Au
collisions at RHIC.
a
Raphaël Granier de Cassagnaca
Laboratoire Leprince-Ringuet, École polytechnique Palaiseau, 91128, France, [email protected]
Heavy quarkonia production is expected to be sensitive to the formation of a quark gluon plasma.
It is also sensitive to cold nuclear matter and subtracting the “normal” suppression is a key point in
any interpretation of quarkonia production in heavy ion collisions. Data from p+A or d+A collisions
provide good insights into the various effects cold nuclear matter has on quarkonia (shadowing,
absorption, etc.) To extrapolate them to A+A collisions, one always rely on models. After a quick
review of models used so far, I will present a new Glauber-inspired approach. It uses the first
centrality dependent d+A quarkonia measurement, namely J/ψ in d+Au collisions seen by the
PHENIX experiment to derive the Au+Au nuclear modification factor in a as much as possible
model-independent way.
References
[1] R. Granier de Cassagnac, Hard Probes 2006 (a preview of the model can be found in a review talk given at this
conference, available at
http://www.phenix.bnl.gov/WWW/publish/raphael/Talks/2006.06.13.HP2006.Raphael.pdf ).
142
A measurement of the centrality dependence of the NΩ/Nφ ratio and φ anisotropic flow
- a test of thermalization in Au+Au collisions at RHIC
S-L. Blytha for the STAR Collaboration
Nuclear Collisions Group, Lawrence Berkeley National Laboratory
Berkeley, CA, 94703, USA, [email protected]
aRelativistic
Due to its long lifetime and relatively small hadronic interaction cross-section, the φ-meson is a
clean probe for studying the properties of the hot and dense medium created in high-energy nuclear
collisions. In this talk, we present the first results of the centrality dependence of the N (Ω)/N (φ)
ratios and φ anisotropic flow (v2) from Au+Au collisions at RHIC. Results are extracted from RHIC
run-IV Au+Au collisions at 200 GeV using the STAR detector. The φ spectra and v2 have been
measured up to pT ∼ 5 GeV/c at mid-rapidity. The combination of the high pT reach and systematic
results from other hadrons can provide information on the medium properties. For more central
collisions, the eccentricity-scaled anisotropic flow (v2/  ) is large, indicating a stronger collective
expansion in the early partonic stage. For pT > 2 GeV/c, the v2 values are consistent with the v2
values of other mesons, a signature of parton coalescence[1]. In addition, the N (Ω)/N (φ) ratio is
found to increase linearly as a function of pT , a characteristic of coalescence of thermal quarks[2]
for both φ and Ω. In the most central collisions, the linear increase reaches up to pT ∼4 GeV/c
implying that most of the multistrange hadrons are formed directly from thermalized s-quarks in
Au+Au collisions at RHIC.
References
[1] S. Voloshin, Nucl. Phys. A 715, 379(2003), Y. Nonaka et al. Phys. Lett. B 583 (2004) 73.
[2] R. Hwa and C. Yang, nucl-th/0602024, L-W. Chen and C. M. Ko, Phys. Rev. C 73 (2006) 044903.
143.
Transverse momentum broadening of heavy quarkonium production
Zhongbo Kanga and Jian-Wei Qiub
Department of Physics and Astronomy, Iowa State University
Ames, Iowa 50011, USA, [email protected] [email protected]
could be a good probe for properties of nuclear medium and play an important role in understanding the novel nuclear dependence recently observed in relativistic heavy ion collisions.
Although the amount of broadening due to each soft rescattering is too weak a
scale to warrant a reliable calculation, an averaged broadening in a hard collision could be a
physical quantity calculable in QCD perturbation theory [1].
71
T
In Ref. [2], Drell-Yan transverse momentum broadening
was calculated in
perturbative QCD by evaluating soft rescattering diagrams between incoming (anti)quark and the
nuclear matter. The broadening was shown to be proportional to the target size or have the A1/3
type nuclear dependence, and it was consistent with both Fermilab and CERN data. However, as
pointed out in Ref. [3], there have been difficulties in understanding the same broadening in the
production of heavy quarkonia (J/ψ and  ). Since heavy quarkonium is mainly produced by
gluon-gluon fusion, while Drell-Yan by quark-antiquark annihilation, it was expected that the ratio
of broadening of heavy quarkonium over Drell-Yan is close to CA/CF = 2.25, the ratio of color
factors of gluon and quark rescattering. Although the broadening of heavy quarkonium in
hadron-nucleus collisions shows the same A1/3 type nuclear dependence, the ratio could be as large
as 5, twice of the naive expectation [3].
Since a heavy quarkonium is unlikely to be formed at the same time when the heavy quark pair
was produced, the final-state interaction between the pair and the medium could generate
additional broadening. Because final-state interaction is sensitive to the formation mechanism of the
bound state, we calculate the broadening of heavy quarkonium in both NRQCD and Color
Evaporation Model, and found that although there are some differences in analytical expressions,
these two models produce very similar numerical values for heavy quarkonium broadening. The
value is close to twice of CA/CF at fixed target energies, and is consistent with existing data. We will
also discuss the extension to the collider energies.
References:
[1] J.W. Qiu and G. Sterman, Int. J. Mod. Phys. E12, 149 (2003).
[2] X. Guo, Phys. Rev. D58, 114033 (1998).
[3] J.C. Peng, arXiv:hep-ph/9912371.
144.
Quarkonium Production in STAR
P.~Djawotho for the STAR Collaboration
Indiana University Cyclotron Facility
2401 Milo B. Sampson Lane, Bloomington, Indiana 47408, USA, [email protected]
In the hot and dense matter produced in relativistic heavy-ion collisions, the creation of a
quark-gluon plasma is expected to modify the production of quarkonia, significantly suppressing
their yields. As a baseline for any estimate of suppression, the production in p+p collisions is
mandatory. We present preliminay results on $J/\psi$ and $\Upsilon$ measurements in p+p
collisions at $\sqrt{s}=200$ GeV via the dielectron decay channel in the midrapidity region. A
dedicated trigger was used to enhance the quarkonia samples. We compare the results to
perturbative calculations and previous measurements.
145.
Elliptic flow of electron from heavy flavor decay by the PHENIX
Shingo Sakai for the PHENIX Collaboration
University of Tsukuba
Charm and bottom quarks are believed to be produced in initial collisions via gluon fusion and
to propagate through the hot and dense medium created in the collisions. Therefore they can be a
powerful probe to study the medium created in heavy ion collisions. One of the biggest discoveries
at RHIC is that the elliptic flow (v2) for light hadrons, such as pions and kaons, scales with the
number of constituent quarks. This scaling behavior is consistent with the predictions of the quark
coalescence model, which assumes a finite v2 of light quarks such as u quark and s quark. Charm
and bottom production can be studied by measuring electrons from their semi-leptonic decays in the
PHENIX experiment at RHIC. A recent measurement of electron v2 from semi-leptonic charm
decay at PHENIX shows large v2 in Au+Au collisions at
. The v2 of the electrons is
consistent at low pT with the predictions of a model that assumes charm quark flow. This
consistency would suggest that the charm quarks also flow. In addition to charm flow, electron
72
yields from charm and bottom decay also suggest that the heavy quark energy loss is larger than
expected in the medium created in Au+Au collisions, indicating a stronger than expected interaction
of with the medium. In this presentation we will show the latest results on v2 of heavy favor
semi-leptonic decay electrons measured at PHENIX, including the final results for 200GeV Au+Au
collisions.
IV.
Direct Photons, Dileptons and Vector Mesons
146.
IN RELATIVISTIC NUCLEAR COLLISIONS
G. Y. Qina, C.Galea, and A. Majumderb
Department of Physics, McGill University,Montreal, QC, H3A 2T8, Canada [email protected]
bDepartment of Physics, Duke University,Durham, NC 27708-03051, USA [email protected]
a
In a medium where charge conjugation symmetry is spontaneously broken, processes
that are usually forbidden because of Furry's theorem can occur. Consequently, in a hot
plasma containing a residual charge density, processes that contain a virtual quark (antiquark)
loop like gluon fusion and decay may now proceed with a lepton pair or real photon signature.
We investigate those in Hard Thermal Loop effective theory and point out their observable
properties at RHIC and at the LHC. In particular, we investigate the sensitivity of the
channels to departures from chemical equilibrium at early times and high temperatures.
Similarly, the situation where one of the initial state partons is a hard QCD jet is considered,
together with its electromagnetic signature. It is found that in some regions of phase space,
the new processes outshine those associated with the leading order term.
References:
[1] A. Majumder, A. Bourque, and C. Gale, Phys. Rev. C 69, 064901 (2004).
[2] G. Y. Qin, A. Majumder, and C. Gale, to be submitted (2006).
147.
Thermal Radiation from Au + Au Collisions at
Alama,
Nayaka,
s =200 GeV/A Energy
Royb,
Jan-e
Jajati K.
Abhee K. Dutt-Mazumderb and Bikash Sinhaa,b
aVariable Energy Cyclotron Centre, 1/AF, Bidhan Nagar Kolkata 700 064, India [email protected]
bSaha Institute of Nuclear Physics, 1/AF, Bidhan Nagar Kolkata 700 064, India
The transverse momentum distribution of direct photons and (low) invariant mass distribution
of lepton pairs have been studied for Au + Au collisions at s =200 GeV/A. It has been shown that
the data from PHENIX collaboration can be reproduced reasonably well assuming a deconfined
state of thermalized quarks and gluons formed with initial temperature ～400 MeV. The effects of
the modifications of hadronic properties at non-zero temperature have been taken into account in
evaluating the photon and dilepton spectra. The value of the extracted true' (after subtracting the
flow effects) average temperature of the system from the photon spectra is about 215 MeV, which is
more than the value of transition temperature obtained from lattice QCD simulations. The
experimental data on electromagnetic probes have also been contrasted with results obtained within
the framework of N=4 super symmetric Yang-Mills theory [1].
References:
[1] P. Kovtun, Talk at International Conference on Strong and Electroweak Matter, Brookhaven National
Laboratory,May 10-13, 2006; S. Caron-Huot, P. Kovtun, G. Moore, A. Starinets, L. G. Yaffe, hep-th/0607237.
148.
Thermal Dimuon Yields at NA60
K. Duslinga and I. Zahedb
Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY,
11794-3800, USA,
73
a
[email protected], b [email protected]
The recent measurement of excess dimuons at the NA60 experiment have far better statistics
then any previous dilepton measurements, thereby giving larger constraints on any medium
modification to the vector mesons as well as the amount of mixing in the vector/axial correlators
arising due to chiral symmetry restoration. We present the recent results of [1] where the dilepton
rates of [3,4,5] are folded over the spacetime evolution of a fireball based on hydrodynamic
calculations with CERN SPS conditions, resulting in a dimuon yield in good agreement with the
recent measurements reported by NA60 [2].
The dilepton emission rates from the hadronic phase are treated at finite temperature and
baryon density and are completely constrained by broken chiral symmetry in a density expansion.
The rates are expressed in terms of vacuum correlators which are measured in e+e− annihilation, 
decays and photo-reactions on nucleons and nuclei [3,4,5]. The dilepton emission rates from the
sQGP phase originate primarily from qq annihilation with nonperturbative effects due to
non-vanishing gluon condensates [6].
References:
[1] K. Dusling, D. Teaney, and I. Zahed, arXiv:nucl-th/0604071
[2] S. Damjanovic et.al., arXiv:nucl-ex/0510044
[3] J. V. Steele, H. Yamagishi, and I. Zahed, Phys. Lett. B 384 (1997) 255.
[4] J. V. Steele, H. Yamagishi, and I. Zahed, Phys. Rev. D 56 (1997) 5605; Nucl. Phys. A 638 (1998) 495c.
[5] C.-H. Lee, H. Yamagishi, and I. Zahed, Phys. Rev. C 58 (1998) 2899.
[6] C.-H. Lee, J. Wirstam, I. Zahed, and T. H. Hansson, Phys. Lett. B 448, 168 (1999).
149.
THEORETICAL INTERPRETATION OF RECENT SPS DILEPTON DATA
H.van Heesa and R.Rappa
Institute, Texas A&M University
College Station, TX, 77843-3366, USA, [email protected]
aCyclotron
We summarize our theoretical understanding of dilepton spectra with emphasis on recent
measurements in In-In and Pb-Au collisions by NA60 and NA45 at the CERN SPS. Different
theoretical models for the in-medium electromagnetic current-current correlator, including
vector-meson spectral functions and continuum contributions, using a thermal fireball to describe
the evolution of relativistic heavy-ion collisions, are compared to the data.
The low-mass region, M≤0.9 GeV, is well described by vector-meson spectral functions, most
importantly ρ mesons, in hot hadronic matter based on hadronic many-body theory [1]. The
prevalent effects are identified as being due to baryon induced interactions. At higher masses, 0.9
GeV≤M≤1.5 Gev, four-pion contributions are important to describe the observed dimuon access
in this region, indicating effects of the onset of chiral-symmetry restoration (chiral mixing of
isovector-vector and -axialvector currents).
Our investigations also confirm that the contribution from the quark-gluon-plasma phase is
relatively small compared to the hadronic component.
We furthermore apply our approach to investigate recent data for the dilepton-qt spectra. For In-In
collisions a detailed understanding of the dileptons from ρ-meson decays after thermal freeze-out
becomes important, with additional sensitivity to the flow characteristics of the fireball at thermal
freezeout.
References:
[1] H. van Hees, R. Rapp, hep-ph/0603084 and hep-ph/0603084.
150.
DIELECTRON PRODUCTION IN C+C COLLISIONS WITH HADES
G. Agakishiev11, C. Agodi1, A. Balanda5, G.Bellia1,2, D. Belver19, A. Belyaev9, A. Blanco3,M.Böhmer15,
J.L.Boyard17, P.Braun-Munzinger6, P.Cabanelas19, E. Castro19, S. Chernenko9, T.Christ15, M. Destefanis11, J.
Díaz20, F.Dohrmann7, I. Durán19, T. Eberl15, L.Fabbietti15, O. Fateev9, P. Finocchiaro1, P.J.R.Fonte3,4, J. Friese15, I.
Fröhlich10, T.Galatyuk6, J.A. Garzón19, R. Gernhäuser15, C.Gilardi11, M. Golubeva14, D. González-Díaz6,E.
Grosse7,8, F. Guber14, Ch. Hadjivasiliou16, M.Heilmann10, T. Hennino17, R. Holzmann6, A.Ierusalimov9, I. Iori12,13,
74
A. Ivashkin14, M.Jurkovic15, B. Kämpfer7, K. Kanaki7, T.Karavicheva14, D. Kirschner11, I. Koenig6, W.Koenig6,
B.W. Kolb6, R. Kotte7, F. Krizek18, R.Krücken15, A. Kugler18, W. Kühn11, A.Kurepin14, J. Lamas-Valverde19, S.
Lang6, S.Lange11, L. Lopez3, A. Mangiarotti3, J.Maín19, J. Markert10, V. Metag11, B.Michalska5, D. Mishra11, E.
Moriniere17, J.Mousa16, M. Münch6, C. Müntz10, L.Naumann7, R. Novotny11, J. Otwinowski5, Y.C.Pachmayer10,
M. Palka5,6, V. Pechenov11, T.Pérez11, J. Pietraszko6, R. Pleskac18, V.Pospísil18, W. Przygoda5, B. Ramstein17,
A.Reshetin14, M. Roy-Stephan17, A. Rustamov10, A.Sadovsky7, B. Sailer15, P. Salabura5,6, A.Schmah6, P. Senger6,
K. Shileev14, R. Simon6, S.Spataro11, B. Spruck11, H. Ströbele10, J.Stroth10,6, C. Sturm6, M. Sudol10,6, K.Teilab10, P.
Tlusty18, M. Traxler6, R. Trebacz5,H. Tsertos16, I. Veretenkin14, V. Wagner18, H.Wen11, M. Wisniowski5, T.
Wojcik5, J.Wüstenfeld7, Y. Zanevsky9, P. Zumb
1
Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud, 95125 Catania, Italy
2
Dipartimento di Fisica e Astronomia, Università di Catania, 95125, Catania, Italy
3
LIP-Laboratório de Instrumentação e Física Experimental de Partículas, Departamento de Física da
Universidade de Coimbra, 3004-516 Coimbra, PORTUGAL.
4
ISEC Coimbra, Portugal
5
Smoluchowski Institute of Physics, Jagiellonian University of Cracow, 30059 Cracow, Poland
6Gesellschaft für Schwerionenforschung mbH, 64291 Darmstadt, Germany
7 Institut für Kern- und Hadronenphysik, Forschungszentrum Rossendorf, PF 510119, 01314 Dresden,
Germany
8
Technische Universität Dresden, 01062 Dresden, Germany
9
Joint Institute of Nuclear Research, 141980 Dubna, Russia
10Institut für Kernphysik, Johann Wolfgang Goethe-Universität, 60486 Frankfurt, Germany
11II.Physikalisches Institut, Justus Liebig Universität Giessen, 35392 Giessen, Germany
12Istituto Nazionale di Fisica Nucleare, Sezione di Milano, 20133 Milano, Italy
13Dipartimento di Fisica, Università di Milano, 20133 Milano, Italy
14Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow, Russia
15Physik Department E12, Technische Universität München, 85748 Garching, Germany
16Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus
17Institut de Physique Nucléaire d'Orsay, CNRS/IN2P3, 91406 Orsay Cedex, France
18Nuclear Physics Institute, Academy of Sciences of Czech Republic, 25068 Rez, Czech Republic
19Departamento de Física de Partículas. University of Santiago de Compostela. 15782 Santiago de
Compostela, Spain
20Instituto de Física Corpuscular, Universidad de Valencia-CSIC,46971-Valencia, Spain
The HADES spectrometer installed at GSI Darmstadt is a second generation experiment
devoted to study production of di-electron pairs from proton, pion and nucleus induced reactions at
the SIS/Bevelac energy regime. The main goal is to search for in-medium modifications of spectral
functions of the light vector meson ρ/ω at moderate temperatures and nuclear matter densities [1].
Spectroscopy of rare lepton pairs in reactions with abundant hadron production requires an efficient
electron identification. In HADES it is achieved with a large geometrical acceptance (35% for
pairs), fast electron identification in hadron blind RICH accompanied by a set of Pre-Shower and
Time-Of-Flight counters and selective multistage trigger scheme. Particles momentum is measured
by a tracking system consisting of four Mini-Drift-Chambers layers surrounding a toroidal
superconducting magnet.
The detector went successfully into operational in 2002 and since then collected data from
12
C+12C collisions at 2AGeV (2002), 1AGeV (2004) and proton-proton (2004) reactions at 2.2 GeV.
The main goal of the measurement with 12C+12C system is to investigate dielectron enhancement
found in 12C+12C and 40Ca+40Ca collisions at 1 AGeV in the pioneering experiments of DLS
collaboration [2]. The pp experiment focused on exclusive and inclusive η meson production which
contributes to the dielectron invariant mass range of 140 < Me+e- <550 MeV/c2 and therefore
provides important reference for the HI data. In this contribution we would like to focus on the
results obtained from the 12C+12C collisions at 1 and 2 AGeV. Dielectron invariant mass, rapidity
and transverse momentum distributions corrected for reconstruction efficiencies will be shown.
Comparison of experimental distributions to calculations based on a thermal model including
known π0, η production probabilities and expected from the mT scaling ρ/ω contributions will be
presented. Furthermore, effects of the collision dynamics and in-medium vector meson spectral
functions will be discussed via comparison to results of the microscopic UrQMD[3], HSD[4],
RQMD[5]transport calculations.
75
References:
[1] P.Salabura et.al., Nucl.Phys., A749(2005)150c
[2] R. J. Porter et al., Phys. Rev., Lett. 79 (1997)1229
[3] C. Ernst et al., Phys. Rev. C 58, 447 (1998).
[4] W. Cassing and E. L. Bratkovskaya, Phys. Rep. 308, 65 (1999).
[5] K. Shekhter et al., Phys. Rev. C 68, 014904 (2003), M. D. Cozma, C. Fuchs, E. Santini,
A. Faessler, nucl-th/0601059.
151.
What does the ρ-meson do?
NA60's dimuon experiment and in-medium modification of vector mesons.
J.Rupperta, b, T. Renkc,d
Department of Physics, McGill University, Montreal,QC H3A-2T8, Canada
b
Department of Physics, Duke University, PO Box 90305
Durham, NC, 207708, USA [email protected]
c Department of Physics, PO Box 35, University of Jyväskylä
Jyväskylä, FIN-40014, Finland [email protected]
d Helsinki Institute of Physics, PO Box 64 Helsinki, FIN-00014, Finland [email protected]
a
The NA60 collaboration has studied low-mass muon pair production in In-In collisions at 158
AGeV with unprecendented precision. Considerable in-medium modifications of vector mesons are
expected in hot and dense hadronic matter. We present a study of different theoretically proposed
models of these in-medium modification, especially the ρ-meson, compared to the data. We show
that NA60 measurements are a proof of considerable in-medium broadening effects of the ρ-meson.
Of special relevance are different pT-cuts of the M-spectra as well as pT-spectra at fixed mass
measured by NA60 since they provide additional tests of the evolution model and spectral
functions.
An important theoretical question is how the gradual restoration of chiral symmetry leaves its
imprint via in-medium modifications of the vector mesons. While hadronic many-body
calculations indicate considerable broadening effects with only small shifts of the ρ-meson mass,
Brown and Rho proposed that chiral symmetry restoration might primarily be reflected in a scaling
of the vector meson mass with the quark condensate. Therefore we studied what the data can tell
about possible scaling laws of the ρ-meson mass with the chiral condensate. We argue that the
correlation of changes in the mass and the width of the ρ-meson have to be taken into account in
order to test those scaling laws. We also present a calculation for the intermediate-mass region
which provide a further test of the evolution model. We argue that constraints on the in-medium
modifications could even be further tightened and theoretical uncertainties in the modeling of the
medium evolution reduced by an additional experiment measuring the low mass di-muon
production in Pb-Pb collisions at 158 AGeV with the same resolution as provided by NA60 for the
In-In system.
References:
[1] T.Renk and J.Ruppert, hep-ph/0605130
[2] T.Renk and J.Ruppert, hep-ph/0603110
[3] J.Ruppert, T.Renk and B.Müller, Phys. Rev. C 73, 034907 (2006)
[4] J.Ruppert, T.Renk, Phys. Rev. C 71, 064903 (2005)
152.
Measuring Photons and Neutrons at Zero Degree in CMS
Michael Murray for the CMS Collaboration
University of Kansas, Lawrence, KS, USA. E-mail [email protected]
The CMS Zero Degree Calorimeters, ZDCs, will measure photons and neutrons emitted with
|η|>8.6 from from Pb+Pb, p+Pb and p+p collisions at s NN =5.5, 8.8 and 14 TeV respectively. The
calorimeter consists of an electromagnetic part segmented in the horizontal direction and an
76
segmented shower maximum detector being built for luminosity measurements. We will present
detailed results from tests beam measurements taken at the CERN SPS. These data will be used to
extrapolate the utility of the ZDCs to measure photons, and possibly π0 s in p+p and ultra-peripheral
heavy-ion collisions. Data from the hadronic section can be used to estimate the number of
participants in heavy ion-collisions. In addition we will discuss plans to use the detector to measure
the reaction plane, thereby extending the sensitivity of the central detectors in CMS.
153.
NA60 results on charm and intermediate mass dimuons production
in In-In 158 GeV collisions
R.Shahoyan for the NA60 Collaboration
CFTP, Instituto Superior Tcnico
Av. Rovisco Pais, 1699 Lisbon Codex Portugal, [email protected]
One of the aims of the NA60 experiment at the CERN SPS was the clarification of the origin of
the excess of dimuon production with invariant mass in the range 1.2-2.7 GeV/c2 observed by the
NA50 experiment in 158 GeV Pb-Pb collisions. Thanks to a high granularity pixel vertex tracker,
the NA60 experiment is able to match the muons from the Muon Spectrometer to the tracks in the
vertex region and thus to separate dimuon contributions from prompt production and from open
charm decays. Our data sample of 158 GeV In-In collisions has led already to preliminary results,
based on a partial set of data, which show that the excess is due to prompt dimuons. We present
here the most recent results obtained with full statistics and, moreover, after final alignment of the
detectors, which strongly improves the off-vertex decay tagging capabilities of NA60. Results on
multiplicity and Pt dependence of both charm and prompt dimuon contributions are presented here
for the first time.
154.
New results on the ρ spectral function in Indium-Indium collisions
J. Seixasa (on behalf of NA60 Collaboration)
Laboratório de Intrumentação e Física Experimental de Partículas,
Av. Elias Garcia 14, 1o, 1000-149 Lisboa, Portugal, [email protected]
a
The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 AGeV In-In
collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays.
The unprecedented sample size of close to 400K events and the good mass resolution of about 2%
have made it possible to isolate the excess by subtraction of the decay sources (keeping the ρ). The
shape of the resulting mass spectrum shows some nontrivial centrality dependence, but is largely
consistent with a dominant contribution from π+ π- → μ+μ- annihilation. The associated ρ spectral
function exhibits considerable broadening, but essentially no shift in mass. The
acceptance-corrected transverse-momentum spectra have a shape atypical for radial flow, but also
show a significant mass dependence, pointing to different sources in different mass regions. The
results are shortly compared to theoretical model predictions.
155.
Photon-tagged correlations from RHIC to LHC
François Arleoa
aCERN PH department, TH division, 1211 Geneva 23, Switzerland, [email protected]
Single pion and prompt photon large transverse momentum spectra in p–p and Au–Au
collisions are computed in perturbative QCD at RHIC energy, s = 200 GeV. Next-to-leading
order calculations are discussed and compared with p–p scattering data. Subsequently, quenching
factors are computed to leading order for both pions and photons within the same energy loss model.
The good agreement with PHENIX preliminary data allows for a lower estimate of the energy
density reached in central Au-Au collisions, ∈>10 GeV/fm3. Double inclusive photon-pion
production in p–p and Au–Au collisions is then addressed. Next-to-leading order corrections prove
rather small in p-p scattering. In Au-Au collisions, the quenching of momentum-correlation spectra
77
is seen to be sensitive to parton energy loss processes, which would help to understand how the
fragmentation dynamics is modified in nuclear collisions at RHIC. Finally, we explore similarly
photon–pion and photon–photon momentum correlations in p–p and Pb–Pb scattering at LHC
energy.
References:
[1] F. Arleo, P. Aurenche, Z. Belghobsi, J.-P. Guillet, JHEP 11 (2004) 009
[2] F. Arleo, hep-ph/0601075.
156.
HIGH MOMENTUM DILEPTON PRODUCTION FROM JETS IN
A QUARK-GLUON PLASMA
S. Turbidea, C.Galea, D. K. Srivastavab and R. Friesc
Department of Physics, McGill University,Montreal, QC, H3A 2T8, Canada [email protected]
b
Variable Energy Cyclotron Centre,1/AF Bidhan Nagar, Kolkata 700 064, India [email protected]
cSchool of Physics and Astronomy, University of Minnesota
Minneapolis, MN 55455, USA [email protected]
a
We discuss the emission of high momentum lepton pairs in central Au+Au collisions at RHIC
( s NN =200 GeV) and Pb+Pb collisions at the LHC ( s NN =5500 GeV). Yields of dileptons
produced through interactions of jets with thermal partons have been calculated, with
next-to-leading order corrections through hard thermal loop (HTL) resummation. They are
compared with thermal dilepton emission and with the Drell-Yan process. A complete leading order
(in αs) treatment of jet energy loss has been included. Jet-plasma interactions are found to dominate
over thermal dilepton emission for all values of the invariant mass M. Drell-Yan is the dominant
source of high momentum lepton pairs for M>3 GeV at RHIC, after the background from heavy
quark decays is subtracted. At LHC, the range M<7 GeV is dominated by jet-plasma interactions.
The effect of hydrodynamic flow is taken into account.
References:
[1] S. Turbide, C. Gale, D. K. Srivastava, and R. J. Fries, Phys. Rev. C 74, 014903 (2006).
157.
Direct photon production at both initial partonic and final hadronic states in p + p and Au
+ Au collisions at top RHIC energy
Ben-Hao Saa and Dai-Mei Zhoub
a China Institute of Atomic Energy P. O. Box 275 (18), Beijing, 102413 [email protected]
bInstitute
of Particle Physics, Huazhong Normal University Wuhan, Hubei, 430079, P. R. China,
[email protected]
both the partonic and hadronic stages of p+p and Au + Au collisions at top RHIC energy. The Double
ratio of γtot/π0 (total γ) to γdec/π0 (decay γ) is calculated in pure hadronic scenario for both the p+p and
Au+Au collisions and in scenario of final hadronic state developed from initial partonic stage for
Au+Au collisions. The corresponding results are symboled, respectively, by”HM” and”HM v.
QGM” (here”v.” means via). In addition, the direct photon production in initial pure partonic state
(”QGM”) of Au + Au collision is investigated and compared to the”HM v. QGM” and ”HM”,
respectively. Prompt direct photon (produced in hard process of nucleon- nucleon collision), the
thermal direct photon (q q → gγ, qg → qγ in parton cascade process), and the hadronic direct photon
(π +π → ρ+γ and π + ρ → π + γ in hadronic rescattering) are considered. However, the
nonperturbative direct photon from fragmentation of quark and gluon jets is neglected for the
moment. It turns out that a visible deviation of the double ratio above unity is seen in both the ”HM”
and ”HM v. QGM” simulations, consistent with PHENIX observations [2]. The deviation in ”HM v.
QGM” simulations is somewhat stronger than that in ”HM” simulations. Direct photon production
in ”HM” simulations is close to that in ”HM v. QGM” simulations indicating: the photon produced
in partonic scattering processes is small because those partonic scattering processes are weak in
competing with others and the messages of direct photon are not distorted by the hadronization.
78
References
[1] Dai-Mei Zhou, Xiao-Mei Li, Bao-Guo Dong, and Ben-Hao Sa, Phys. Lett. B, v. 638, p.461-463, 2006.
[2] PHENIX Collaboration., Phys. Rev. D, v.71, 071102, 2005; Phys. Rev. Lett , v. 94, 232301, 2005.
158.
Thermal Dilepton Production from Dropping ρ
based on the Vector Manifestation
Department of Physics, Nagoya University,
Nagoya, 464-8602, Japan, [email protected]
bGesellschaft für Schwerionenforschung (GSI), 64291 Darmstadt, Germany, [email protected]
a
Changes of hadron masses are indications of chiral symmetry restoration occurring in hot
and/or dense QCD [2]. Dropping masses of hadrons following the Brown-Rho (BR) scaling [3] can
be one of the most prominent candidates of the strong signal of melting quark condensate qq
which is an order parameter of spontaneous chiral symmetry breaking. We study the pion
electromagnetic form factor and the dilepton production rate in hot matter using the hidden local
symmetry theory as an effective field theory for pions and ρ mesons. In this framework, the chiral
symmetry restoration is realized as the vector manifestation (VM) in which the massless vector
meson becomes the chiral partner of the pion [4,5], giving a theoretical framework of the dropping
ρ à la BR scaling. In the VM the vector dominance (VD) is largely violated near the phase transition
point associated with the dropping ρ. We present the effect of the violation of the VD to the
dilepton production rate and make a comparison with the one predicted by assuming the VD
together with the dropping ρ.
Based on the work done in Ref.[1].
References:
[1] M.Harada and C.Sasaki, to appear.
[2] V.Bernard and U.G.Meissner, Nucl. Phys. A 489, 647 (1988); T.Hatsuda and T.Kunihiro, Phys. Rept. 247, 221
(1994); R.D.Pisarski, hep-ph/9503330; R.Rapp and J.Wambach, Adv. Nucl. Phys. 25, 1 (2000); F.Wilczek,
hep-ph/0003183; G.E.Brown and M.Rho, Phys. Rept. 363, 85 (2002).
[3] G.E.Brown and M.Rho, Phys. Rev. Lett. 66, 2720 (1991).
[4] M.Harada and K.Yamawaki, Phys. Rev. Lett. 86, 757 (2001); Phys. Rept. 381, 1 (2003).
[5] M.Harada and C.Sasaki, Phys. Lett. B 537, 280 (2002); M.Harada, Y.Kim and M.Rho, Phys. Rev. D 66,
016003 (2002).
159.
Improved Quark Mass Density-dependant model with quark and ω, σ meson couplings and
the deconfinement phase transition of nuclear matter
Ru-Keng Su
Department of Physics, The Fudan University, Shanghai, 200433, P. R. China, [email protected]
An improved quark mass density- and temperature- dependent model which includes the
couplings between quarks and the σ-mesons, ω-mesons is suggested. The MIT bag boundary
constrain has been given up and the interactions between quarks and mesons are extended to the
whole free space. We show that the present model is successful to describe both the saturation
properties and the deconfinement phase transition of nuclear matter. When the effective nucleon
masses vanish and the bag radius tends to infinite, the quark deconfinement phase transition takes
place. The corresponding QGP phase diagram is addressed.
References:
(I) Quark mass density- and temperature dependant model
[1] Y. Zhang, R. K. Su, S. Q. Ying and P. Wang, Europhys.Lett., 56, 361, (2001).
[2] Y. Zhang and R. K. Su, Phys. Rev. C65, 035202, (2002); Phys. Rev. C67, 015202, (2003); J. Phys. G30, 811,
(2004); Mod. Phys. Lett. A18, 143, (2003).
[3] J. Y. Shen, Y. Zhang, B. Wang and R. K. Su, Int. J. Mod. Phys. A20, 7547, (2005).
(II) Quark mass density-dependant model with quark and non-linear scalar field coupling
[4] C. Wu, W. L. Qian and R. K. Su, Phys. Rev. C72, 035205, (2005); Chinese Phys. Lett. 22, 1866, (2005).
[5] H. Mao, R. K. Su and W. Q. Zhao, "Soliton solution of the improved quark mass density-dependant model at
79
finite temperature".
(III) Present model
[6] W. L. Qian and R. K. Su, nucl-th/0509006
160.
MEDIUM MODIFICATION ON VECTOR MESONS IN 12 GeV p + A REACTIONS
M.Naruki a, H.En'yo, R.Muto, T.Tabaru and S.Yokkaichi
RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan, [email protected]
Y.Fukao, H.Funahashi, M.Ishino, H.Kanda, M.Kitaguchi, S.Mihara, K.Miwa, T.Miyashita, T.Murakami,
T.Nakura, F.Sakuma, M.Togawa, S.Yamada and Y.Yoshimura
Department of Physics, Kyoto University, Kitashirakawa Sakyo-ku, Kyoto 606-8502, Japan
J.Chiba, M.Ieiri, O.Sasaki, M.Sekimoto and K.H. Tanaka
Institute of Particle and Nuclear Studies, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
H.Hamagaki and K.Ozawa
Center for Nuclear Study, Graduate School of Science,
University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
a
We present the final results which show ρ, ω, and  meson mass modifications at normal
nuclear density in KEK-PS E325 experiment. The invariant mass spectra of e+e- pairs produced in
12GeV proton-induced nuclear reactions are measured at the KEK Proton-Synchrotron. We
observed the significant excesses over the known hadronic sources at the low-mass side of the
omega peak on the e+e- invariant mass spectra. Without mass modification, the 95% C.L. allowed
regions for the production ratios of ρ to ω are obtained as ρ/ω< 0.15 and ρ/ω< 0.31 for C and Cu
targets, respectively. A possible explanation is that most of the ρ are decaying inside the nuclei due
to their short lifetime; their mass is modified in nuclear media and contribute to the excess. We
examined that the observed excess can not be explained by the ρ/ω interference nor the different
parameterizations of the ρ line shape like the non-relativistic Breit-Wigner, the Gounaris-Sakurai
shape and the relativistic Breit-Wigner shape multiplied by the Boltzmann factor [1].
As for the  meson, both results obtained from C and Cu targets were consistent with the
simulation shape which included no spectral modification in the high βγ region (βγ > 1.75). On the
other hand, in the low βγ region (βγ < 1.25), significant enhancement on the low-mass side of the
 meson peak was observed in the Cu data. This results suggest the  meson modification in
nuclei [2]. At the low-mass side of ω peak, the observed excesses are consistent with the model
calculation taking into account the 9% mass decrease at normal nuclear density, as theoretically
predicted. For the  meson, spectra in each βγ regions can be understood by the model calculation
assuming 4% mass decrease and 4 times width broadening at normal nuclear density. We therefore
conclude that the vector meson modification in a dense matter is experimentally verified.
References:
[1] M. Naruki et al. Phys. Rev. Lett. 96(2006)092301
[2] R. Muto et al. nucl-ex0511019
161.
Vector meson spectral function in asymmetric nuclear matter
P. Roya, A. K. Dutt-Mazumdera, S. Sarkarb, J. Alamb
Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata - 700 064, India,
[email protected]
b Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata - 700 064, India, [email protected]
a Saha
It is well known that the spectral behaviour of light vector mesons change in hot and/or dense
nuclear matter. In comparatively low energy experiements highly dense baryonic matter may be
produced with large neutron(n)-proton(p) asymmetry. Such an environment allows us to study
various exclusive medium dependent processes. Large n-p asymmetry will lead to the mixing of the
ρ and ω mesons because of the ground state induced isospin symmetry breaking. We show that the
mixing could be substantial and will affect the dilepton production rate via the baryon density and
asymmety dependent pion form factor. Thus compressed baryonic matter might be useful to
determine such in-medium pion form factor. Such mixing will also be relevant for the study of
80
density dependent charge symmetry violating part of the nucleon-nucleon interactions.
References:
[1] A. K. Dutt-Mazumder, B. Dutta-Roy, A. Kundu Phys. Lett B 399, p-196, 1997.
162.
Low mass dielectron measurements at J-PARC
S.Yokkaichi a, K.Aokie, H.En'yoa, H.Hamagakib, M.Narukia, R.Mutoa, K.Ozawab,
a
RIKEN 2-1, Hirosawa, Wako, Saitama, 351-0198, Japan [email protected]
b
CNS, Graduate School of Science, Univ. of Tokyo
7-3-1, Hongo, Tokyo, 113-0033, Japan
c Graduate School of Science, Hiroshima Univ.
1-3-1, Kagamiyama, Higashi-hiroshima, Hiroshima, 739-8526, Japan
d
High Energy Accelerator Research Organization (KEK)
1-1, Oho, Tsukuba, Ibaraki, 305-0801, Japan
e
Department of Physics, Kyoto Univ.
Kitashirakawa, Sakyo-ku, Kyoto, 606-8502, Japan
We proposed a new experiment at J-PARC 50 GeV Proton Synchrotron. We intend to measure
the low-mass dielectron spectrum in 30/50 GeV p+A reaction to investigate the restoration
of chiral symmetry in the finite density environment. This experiment is designed to collect
roughly 105 of  mesons in e+e- channel with 10 MeV/c2 of mass resolution, and more statistics
for the ρ and ω mesons. This statistics is approximately 100 times as large as that achieved by the
KEK--PS E325 experiment, which already observed the signatures of modification of e+e- invariant
mass spectra in both of ρ/ω and  -meson mass regions through the 12 GeV p+C and p+Cu reaction.
In  -meson region, small excess is observed at low mass side of  -meson peak only for the
smaller velocity mesons from the larger (i.e. Cu) target, while, in ρ/ω region, excesses over the
known hadronic sources are observed at low mass side of ω meson peak for both targets.
With this high statistics, we are able to measure the momentum/velocity dependence of mass
modification more precisely than E325 case, as well as to confirm the existence of modification in ρ
and/or ω and  -meson spectra. Also the high statistics capability enable us to use larger nuclear
target as lead, which should be thinner than smaller nuclear target case because the larger radiation
length of heavier target material causes worse S/N in the e+e- spectra. On the other hand, smaller
target as proton also can be used with the subtraction method using hydrocarbon and carbon target.
Furthermore, in the larger target case, collision centrality can be determined by the charged particle
multiplicity. Such systematic studies of momentum/velocity dependence, target nuclear-size
dependence and centrality dependence of the mass modification help us to discuss the origin of the
modification by the comparison of the data and many theoretical predictions. Here, we present the
design of new spectrometer, status of detector R&D and the expected signals based on the proposal
submitted to the J-PARC PAC.
163.
PARTON TRANSVERSE MOMENTA AND DIRECT PHOTON PRODUCTION
A.Szczureka,b and T.Pietryckia
of Nuclear Physics, PL-31-342 Cracow, Poland, [email protected]
b University of Rzeszów, PL-35-959 Rzeszów, Poland
a Institute
The invariant cross sections for direct photon production in hadron-hadron collisions are
calculated for several initial energies (ISR, SppS , RHIC, Tevatron, LHC) including intial parton
transverse momenta within the formalism of unintegrated parton distributions (UPDF). Different
approaches from the literature are compared and discussed. A special emphasis is put on the
Kimber-Martin-Ryskin (KMR) distributions and their extension into the soft region. Sum rules for
UPDFs are discussed in detail. We find a violation of naive number sum rules for the KMR UPDFs.
An interesting interplay of perturbative (large kt2) and nonperturbative (small kt2) regions of UPDFs
81
in the production of both soft and hard photons is identified. Off-shell effects are discussed and
quantified. Predictions for the CERN LHC are given. Very forward/backward regions in rapidity at
LHC are discussed and a possibility to test unintegrated gluon distributions (UGDF) is presented.
This part of the presentation is based on [1]. The differences of the cross sections for pp, pn and nn
collisions at SPS and RHIC are discussed. Their effect on nuclear modification factor is calculated.
A kinematical correlations in azimuthal angle and the length of the transverse momenta between the
photon and an associated jet is studied and discussed. A new observables to test UPDFs are
presented.
References:
[1] T.Pietrycki and A.Szczurek, hep-ph/0606304.
164.
Observation of ∆φ∆η Scaled Correlation Signals which increase with Centrality of Au Au collisions
at sNN =200 Gev
aBrookhaven
R.S. Longacrea for STAR Collaboration
National Laboratory, Upton, NY 11973, USA1
We report charged-particle pair correlation analyses in the space of ∆φ (azimuth) and ∆η
(pseudo-rapidity), for minimum bias Au + Au collisions in the mid-transverse momentum range
(0.8<pt<4.0GeV/c) at sNN =200GeV measured in the STAR detector. The analyses involve
unlike-sign charge pairs and like-sign charge pairs, which are transformed into charge-dependent
(CD) signals and charge-independent (CI) signals. We present detailed parametrizations of the data.
We also use a multiplicity scaling to compare the different centralities. We find the signals increase
with increasing centrality. A model featuring dense gluonic hot spots as first proposed by van
Hove[1] predicts that the observables under investigation would have sensitivity to such a
substructure should it occur. A blastwave model including multiple hot-spots motivates the selection
of transverse momenta in the range 0.8< pt <4.0GeV/c. Both CD and CI correlations of high
statistical significance are observed to increase with centrality. A possible interpretation of these
correlation signals involving increased gluonic hot-spots around the surface of the fire ball is
discussed.
References
[1] L.van Hove, Hadronization Quark-Gluon Plasma in Ultra-Relativistic Collisions,CERN-TH (1984) 3924,
L.van Hove, Hadronization Model for Quark-Gluon Plasma in Ultra-Relativistic Collisions, Z. Phys. C27, 135
(1985).
165.
First Measurements of Elliptic Flow Fluctuations
P. Sorensen for the STAR Collaboration
Physics Department, Brookhaven National Laboratory Upton, NY, 11973, USA,
[email protected]
We present first measurements of event-by-event fluctuations of elliptic flow (v2) from the
STAR collaboration. v2 fluctuations may provide valuable insight into the initial conditions and
subsequent dynamic processes in heavy ion collisions. In particular, it’s possible that v2 fluctuations
could help to distinguish experimentally between Color Glass Condensate initial conditions and
Glauber model initial conditions. v2 fluctuations are also thought to be sensitive to exotic
phenomena such as cluster formation and filamentation instabilities. We have extracted v2
fluctuations using several analysis techniques. In particular, we’ve used the multiplicity dependence
of the q-distribution to simultaneously extract v2, the non-flow parameter g2, and v2 fluctuations
(δv2). The measurement of g2 and δv2 allows us to significalty reduce the systematic uncertainty on
the integrated v2 vs centrality at RHIC.
166.
Is There A Mach Cone? – Three-Particle Azimuthal Correlations from STAR
82
Claude A. Pruneau, for the STAR Collaboration
Physics and Astronomy Department, Wayne State University,666 West Hancock, Detroit, MI 48152
USA. [email protected]
Two-particle azimuthal correlations in central Au+Au collisions have shown broadened and
softened away-side correlations when compared to peripheral Au+Au, d+Au and pp collisions.
This could be explained by different scenarios such as: large angle gluon radiation, deflected jets
by transverse flow and/or pathlength dependent energy loss, Cherenkov ra- diation of fast moving
particles, and conical flow generated by hydrodynamic Mach cone shock-waves. Three-particle
azimuthal correlations are needed to discriminate between conical emission and other production
mechanisms. Additionally, variations in the particle pT can possibly be used to distinguish
between conical flow and Cherenkov radiation. In this talk, we present results from STAR on
3-particle azimuthal correlations for a high p⊥ trigger particle with two softer particles. Results
are shown for pp, d+Au and high statistics Au+Au collisions at sNN =200GeV. Two different
methods for obtaining the combinatorial background are used and the results compared; both
show non-zero three-particle correlation strengths. Systematic uncertainties on the shapes and
yields of the correlation functions are extensively studied. Implications of the results in terms of
the different physics scenarios are discussed.
167.
Dielectron continuum measurements in √sNN=200 GeV Au+Au and Cu+Cu collisions at
PHENIX
S. Campbella for the PHENIX collaboration
of Physics, SUNY Stony Brook
Stony Brook, NY, 11794, USA, [email protected]
The dielectron continuum is rich in physics signals including vector meson decays, hadron
Dalitz decays, correlated semi-leptonic heavy flavor decays and direct virtual photon emis- sion. It
is sensitive to modifications due to the QCD phase transition, particularly chiral symmetry
restoration and mass shifts or broadening of the rho meson. Comparison between the PHENIX
Au+Au continuum spectra in different centrality classes and the new Cu+Cu continuum spectra
allows an investigation of surface area and volume effects on all dilepton signals. The more central
Au+Au spectrum suggests an excess over the expected reference cocktail of known hadronic
sources, in contrast to the peripheral Au+Au spectrum. The Au+Au analysis will be compared to a
superposition of meson decays and theoretical pre- dictions including those with and without
medium modification of the rho meson. The status
of the Cu+Cu analysis will also be presented.
168.
Systematic Study of High-pT Direct Photon Production with the PHENIX Experiment at
RHIC
T. Isobea for the PHENIX Collaboration
for Nuclear Study, Graduate School of Science, The University of Tokyo 7-3-1 Hongo, Bunkyo,
Tokyo, 940-0041, Japan, [email protected]
aCenter
Direct photons are a powerful probe to study the initial state of matter created in relativistic heavy
ion collisions since photons do not interact strongly once produced. They are emitted in all stages of
the collision: the initial state where photon production can be described by pQCD; the Quark-Gluon
Plasma (QGP) dominated by thermal emission; and the final hadron-gas phase. In addition, high pT
photons are expected to be produced by the interaction of jet partons with dense matter.
The direct photon yields measured in heavy ion collisions by the PHENIX experiment are in
good agreement with a NLO pQCD calculation scaled by the number of binary nucleon collisions
within current experimental errors and theoretical uncertainties. While this suggests that the
initial-hard-scattering probability is not reduced, the agreement with pQCD calculations might just be
a coincidence caused by mutually counterbalancing effects like energy loss and Compton like
83
scattering of jet partons. PHENIX recorded high-statistics Au+Au and Cu+Cu data sets in 2004 and
2005. Combined with p+p data taken in 2005, these new data sets allow to measure direct photons
and to evaluate the nuclear modification up to very high p T. We present the status of the systematic
study of high-pT direct photon production in ultra-relativistic high energy Au+Au and Cu+Cu
collisions.
169.
A systematic study of low and medium pT direct photon production
in the PHENIX experiment
a
D.Peressounkoa for the PHENIX collaboration
RRC ”Kurchatov institute”Kurchatov sq.1, Moscow, 123182, Russia, [email protected]
Direct photons are emitted during the entire evolution of nucleus-nucleus collisions and escape
freely from the initial hot zone, providing the possibility to test directly its properties. At low and
medium transverse momentum, thermal direct photons and those from jet- medium interactions are
expected to dominate and can be used to estimate the temperature and energy density of the hot
matter. The direct photon yield measured in p+p and d+Au collisions at the same energy serves as
a baseline for estimating the contribution of pQCD photons in Au+Au collisions. The PHENIX
experiment has the capability to measure not only real but also virtual photons through e+e− pairs.
PHENIX can apply a variety of measurement techniques ranging from the classical statistical
subtraction and tagging methods to a newly employed technique to measure internal conversions, an
approach based on photon measurement through external conversion in the detector material, and
direct photon HBT correlations. These methods provide important cross checks and complement
each other, extending the transverse momentum range of the measurement. In this talk we present
the latest results obtained by PHENIX on low and medium pT direct photon production in p+p,
d+Au, and Au+Au collisions at √sNN = 200 GeV.
170.
Azimuthal γ-charged-hadron correlations in d+Au and p+p collisions from STAR at √sNN =
200 GeV
Subhasis Chattopadhyay (for the STAR Collaboration)
Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700064; [email protected]
The study of γ+jet events provides unique information about the fragmentation of hard partons
in the hot medium created in heavy ion collisions. While parton-energy loss is expected to modify
the fragmentation of quarks and gluons, photons escape without interacting.
We present an analysis of azimuthal γ-hadron correlations using photons detected with the
Barrel Electromagnetic Calorimeter (BEMC) and charged hadrons with the Time Projection
Chamber in STAR. For the first time, we present a method to enrich the sample of direct photons
using shower shape analysis in the fine-grained Shower Maximum Detector. The near-side yield
is used to further constrain the contribution of isolated direct photons to the trigger sample.
We discuss this separation in detail and extract the away-side yield for gamma-jet events in p+p
and d+Au collisions at RHIC. An outlook for similar analyses in Cu+Cu and Au+Au events will
also be presented.
171.
FLUCTUATIONS, CORRELATIONS AND FINITE VOLUME EFFECTS IN HIC
L. Turko
Institute of Theoretical Physics, University of Wroclaw
Pl. Maksa Borna 9, 50-204 Wroclaw, Poland, [email protected]
Fluctuations and correlations measured in heavy ion collision (HIC) processes give better
insight into dynamical and kinematical properties of the dense hadronic medium created in
84
ultrarelativistic heavy ion collisions. Particle production yields are astonishingly well reproduced by
thermal models, based on the assumption of noninteracting gas of hadronic resonances. Systems
under considerations are in fact so close to the thermodynamic limit that final volume effects can be
neglected at least when productions yields are considered. The aim of the paper is to show that
finite volume effects become more and more important when higher moments, e.g. correlations and
fluctuations are considered. The basic physical characterization of the system described by means of
the thermal model are underlying probability densities that given physical observables of the system
have specied values. The only way to reproduce those probability distribution is by means of higher
and higher probability moments. Those moments are in fact the only quantities which are
phenomenologically available and can be used for the verification of theoretical predictions. Finite
volume effects are also very important for the lattice QCD calculations. Particle yields in HIC are in
fact the rst moments, so they lead to rather crude comparisons with the model. Fluctuations and
correlations are second moments so they allow for the better understanding of physical processes in
the thermal equilibrium. A preliminary exact analysis of the increasing volume effects was given in
[1]. It has been rigorously shown there an influence of O(1=V ) terms for physical observables. A
new class of variables | semi-intensive quantities was introduced. Those results completely
explained also ambiguities noted in [2], related to "spurious non-equivalence" of di®erent statistical
ensembles used in the description of HIC.
This paper is devoted to further consequences of O(1=V ) terms for HIC with particular em
phasis put on correlations and fluctuations. A detailed analysis is performed which proves that finite
volume effects are here much more important than for the case of particle pro- duction yield
analysis. It will be also shown that correlations and fluctuations important are also coe±cients at
O(1=V ) terms even in the case of the thermodynamic V ! 1 limit.
References：
[1] J. Cleymans, K. Redlich and L. Turko: Phys. Rev. C 71 047902 (2005);
J. Cleymans, K. Redlich and L. Turko: J. Phys. G 31 1421 (2005)
[2] V. V. Begun, M. Gazdzicki, M. I. Gorenstein and O. S. Zozulya: Phys. Rev. C 70,034901 (2004);
V. V. Begun, M. I. Gorenstein, A. P. Kostyuk and O. S. Zozulya: Phys. Rev. C 71,054904(2005);
V. V. Begun, M. I. Gorenstein and O. S. Zozula: Phys. Rev. C 72,014902 (2005); A. KerÄanen,
F. Becattini, V.V. Begun, M.I. Gorenstein, O.S. Zozulya, J. Phys. G 31, S1095 (2005)
172.
Study of non-thermal phase transition inrelativistic nuclear collisions
Department of Physics, Aligarh Muslim University, Aligarh-202002, India
*E-mail: [email protected]
The self-similar cascade mechanism in multiparticle production is not consistent with particle
creation during one phase, but instead requires a non-thermal phase transition. It has been observed
that the signals of non-thermal phase transition can be characterized with the help of a parameter λq.
q  1
The function, λq, is related to the qth order intermittency index as q 
. The values of the
q
intermittency index, αq, obtained from the slopes of graph plotted between ln<Fq> vs. ln M for both
the type of interactions.
In the present paper a modest attempt is made to study the existence of non-thermal phase
transition in the interactions of 28Si and 12C nuclei at 4.5A GeV/c with nuclear emulsion using the
method of Scaled Factorial Moments (SFMs), Fq. For this purpose, two stacks of BR-2 emulsion
exposed to 4.5A GeV/c silicon and carbon beams at Synchrophasotron of Joint Institute of Nuclear
Research (JINR), Dubna, Russia, have been utilized. The experimental result has also been
compared with Lund FRITIOF generated data. The analysis of SFMs gives an evidence for an
intermittency pattern of fluctuations. The results for experimental data are quite consistent with
those obtained for Lund FRITIOF data. The minimum value of λq for qc = 5 is clearly observed in
85
Si interactions with emulsion and AgBr targets. Hence the result on Silicon data for certain value
of q indicates the presence of non-thermal phase transition in these interactions whereas no such
phase transition has been observed for Carbon data.
28
173.
From Di-hadron correlations to parton intrinsic transverse momentum
G. Pappa, G. Faib and P. Lvéaic
a
Institute of Physics, Eötvös University, Budapest, H-1518 Pf. 32, Hungary, [email protected]
b
CNR, Department of Physics, Kent State University, Kent, OH 44242, USA, [email protected]
c
RMKI KFKI, Budapest, H-1525 Pf. 49., Hungary,[email protected]
Recently, the jet structure has been extensively studied at RHIC, in order to unreveal the
properties of the high-energy phase created in relativistic nuclear collisions [1]. Two-jet events, in
particular, allow the study of the centrality dependence of jet suppression (jet quenching) in d+Au
and Au+Au collisions. Moreover, the width of the back-to-back peaks in the correlation between
proton-proton collisions. The width in azimuthal angle has been used at ISR and RHIC energies to
learn about the fragmentation of jets initiated in hard parton collisions. Our focus here will be on
difference between the width of the near-side and away-side peaks, which can be understood in
terms of transverse momentum imbalance. This imbalance originates in the intrinsic transverse
momenta of partons in the proton and in processes that complicate 2  2 skeleton kinematics.
Such processes partially randomize the strong initial parton-parton correlations [2]. We connect the
measured di-hadron correlation widths to the width of the intrinsic transverse momentum
distribution of the partons in the proton. Our simplified and transparent model is able to account for
the trigger-dependence of the transverse momentum width observed in some data. We propose a
new method to evaluate the data on near and away-side correlations. At s = 200 GeV we find a
value forthe transverse momentum width of partons in the proton in good agreement with the values
extracted from pion spectra.
References：
[1] Quark Matter 2005, Budapest, Hungary, http://qm2005.kfki.hu
[2] P. Levai, G. Fai, G. Papp, Phys. Lett. B634, 383, 2006.
174.
Event-by-event pT fluctuations and multiparticle clusters in relativistic collisions
W. Broniowskia;b, B. Hillerc, W. Florkowskia;b and P. Bozeka
of Physics, Świȩtokrzyska Academy, ul. Świȩtokrzyska 15, PL-25406 Kielce, Poland
bThe H. Niewodniczan
ski Institute of Nuclear Physics, Polish Academy of Sciences
PL-31342 Kraków, Poland
cCentro de Fisica Teórica, Departamento de Fisica, University of Coimbra,P-3004-516 Portugal
a Institute
The RHIC analysis of the event-by-event fluctuations of the transverse momentum is explored
and we point out a few remarkable features: 1) the mean and the variance of the inclusive
momentum distribution are practically constant in the reported centrality range 0-30%, 2) the
variance of the average momenta for the mixed events is, as expected, equal to the variance of the
inclusive distribution devided by average multiplicity, and most importantly 3) the difference of the
experimental and mixed-event variances of average pT , denoted as  dyn 2 scales as inverse
multiplicity. The scaling 3) prohibits the jet explanation of the data at medium momenta, where no
dependence on multiplicity should occur. A possible explanation of the observed correlations comes
from clustering in the expansion velocity: matter expands in \lumped clusters" of chunks of matter,
having close collective velocity within a cluster, which induces correlations. Moreover, we show
that value of  dyn 2 is large at the expected scale provided by the variance of pT , which indicates
that the clusters should contain at least several particles in order to enhance the combinatorics.
Finally, we make some estimates of the dynamical value of the correlations in thermal models.
86
References：
[1] W. Broniowski, B. Hiller, W. Florkowski, and P. Bozek, Phys. Lett. B635 (2006) 290
175.
Characteristic form of boost-invariant and cylindrically non-symmetric hydrodynamic
equations
M. Chojnackia and W. Florkowskia;b
PL-31342 Kraków, Poland
b Institute of Physics, Świȩtokrzyska Academy,ul. Świȩtokrzyska 15, PL-25406 Kielce, Poland
a
We consider the hydrodynamics of the perfect fluid and show that the boost-invariant and
cylindrically non-symmetric relativistic hydrodynamic equations for baryon-free matter may be
comfortably reduced to only two coupled differential equations. The effects of the cross- over phase
transition may be included in this scheme by the use of the temperature dependent sound velocity
cs(T). As long as the function cs(T) satisfies the stability condition against the shock formation, the
resulting equations may be solved with the help of standard numerical methods and the proposed
scheme allows for a very convenient analysis of the cylindrically non-symmetric hydrodynamic
expansion. The proposed method may be used to describe the evolution of matter produced in the
central region of ultra-relativistic heavy-ion collisions, such as investigated in the present RHIC or
future LHC experiments.
References：
[1] M. Chojnacki and W. Florkowski, nucl-th/0603065
the videos presenting our hydrodynamic evolution are available
176.
FEMTOSCOPY IN HYDRODYNAMICS INSPIRED MODELS WITH SINGLE
FREEZE-OUT
aFaculty
A. Kisiela
of Physics, Warsaw University of Technology, Warsaw, 00-662, Poland, [email protected]
Hydrodynamics-inspired models with single freeze-out are studied with special emphasis on
femtoscopic observables. The Monte-Carlo implementation[1] of the model is used. E®ects of the
choice of the freeze-out hypersurface and resonance decays in relativistic heavy-ion colli- sions at
RHIC energies are studied in detail. Both identical particle interferomery results for pions and
kaons[2] (\HBT" radii") as well as non-identical particle femtoscopy (system size and emission
asymmetries) for pion-kaon, pion-proton and kaon-proton pairs are studied. All well-established
hadronic resonances are included in the analysis as their role is crucial at large freeze-out
temperatures. We discuss the influence of the short-lived resonance prop- agation on the radii and
the interplay between spatial shift coming from radial flow and time delay coming from resonance
propagation on the emission asymmetries. Using the combined results of all studied pair types we
try to disentangle the two effects.
We compare results to the RHIC data [3] and find that the pion HBT data are fully com- patible
with the single freeze-out scenario. The longitudinal radius is found to be especially sensitive to the
shape of the freeze-out hypersurface, and the data is shown to be favoring the shape for which the
transverse radius is decreasing with time. This means that freeze-out of the fireball occurs
outside-in, which is consistent with most hydrodynamics calculations. We also comment on the
validity of Gaussian approximation of two-pion the emission functionand study in detail the shape
of pair separation distributions with and without taking into account the resonance decays. We find
that short-lived resonances influence the low-q part of the correlation function, reducing the
apparent sample purity (the ¸ parameter). We provide a realistic estimate of this effect for RHIC
collisions.Due to the advanced correlation function calculation method employed we are able to
calculate the two-particle Coulomb interaction exactly. By appplying the Bowler-Sinyukov fitting
method commonly used by RHIC experiments to our model correlation functions we are able to
87
estimate the systematic uncertainty of such procedure. It is found to be within few percent for the
radii obtained in RHIC central collisions.
References：
[1] A. Kisiel, T. Taluć, W. Broniowski, W. Florkowski, Comput. Phys. Commun. 174
(2006) 669-687; nucl-th/0504047
[2] A. Kisiel, W. Broniowski, W.Florkowski, J. Pluta, Phys. Rev. C73 (2006) 064902 ;
nucl-th/0602039,
[3] J. Adams et al., STAR, Phys. Rev., C71 (2005) 044906, nucl-ex/0411036
177.
Scale Dependence of Mean Transverse Momentum Fluctuations at Top SPS Energy
a
G. Tsiledakisa for the CERES Collaboration
Physikalisches Institut der UniversitÄat Heidelberg, Heidelberg, 69120, Germany, [email protected]
Non-statistical event-by-event fluctuations of the mean transverse momentum, pT , have been
proposed as a possible signature for the QCD phase transition, in particular for the critical point. A
surprising finding was that a small but practically beam energy independent value was found for the
broad energy range of 40 AGeV SPS beam up to top RHIC energy. Since fluctuations were
characterized so far by one single (integral) number, it was difficult to estimate the many possible
contributions to them.
Taking into account the high available statistics of Pb-Au collisions at 158 AGeV offered by
the CERES experiment combined with the full azimuthal acceptance, a differential study of mean
pT fluctuations is performed, which by allowing to discriminate among various correlation sources,
provides the sensitivity to the fluctuations related to the vicinity of critical point. For the first time at
SPS energy, the charge-dependent mean pT fluctuations have been analyzed as a function of the
angular pair separation, ¢Á, and of the separation in pseudorapidity, ¢´. The results show that the
overall fluctuations are dominated by the short range correlation peak at small opening angles
(near-side'), most probably originating from Bose-Einstein and Coulomb effects between pairs of
particles emitted with similar velocities. Another important contribution is a broad maximum
at ¢Á=180o (away-side') originating from back-to-back (dijet-like) correlations. Concerning the
observed away-side peak, we demonstrate that it comes from high-pT correlations that cannot be
attributed to elliptic flow.
178.
NEW RESULTS ON FLUCTUATIONS AND CORRELATIONS
FROM THE 49NA EXPERIMENT
G. Stefaneka for the NA49 Collaboration
aInstitute of Physics, Świȩtokrzyska Academy, Kielce 25-406, Poland, [email protected]
New results on uctuations and correlations in hadron production in nucleus-nucleus col-lisions
at the CERN SPS energies obtained by NA49 will be presented and discussed. In particular the
following subjects will be addressed. The dependence of the scaled variance of the multiplicity
distribution in the forward domain in Pb+Pb collisions at 158A GeV on the number of projectile
participants shows a non-monotonic behaviour with a maximum at about 30 projectile participants.
This observation is in qualitative disagreement with predictions of string hadronic models (UrQMD,
HSD, VENUS and HIJING). It can be explained assuming either global thermalization of matter at
the early stage of collisions or non-trivial particle correlations at the hadronization stage. The results
on the correlations between mean transverse momentum and multiplicity as well as their relation to
the multiplicity and hpT i fluctuations in Pb+Pb collisions at 158A GeV will be shown and
compared with various models. The energy dependence of the multiplicity and transverse
momentum fluctuations for central Pb+Pb collisions at 20A, 30A, 40A, 80A and 158A GeV was
measured. The scaled variance of the multiplicity distribution for negatively charged hadrons are
signi¯cantly lower than one in agreement with the prediction of the micro-canonical hadron gas
model. The string-hadronic models significantly over-predict the fluctuations at high SPS energies.
All particle species measured to date, ie. pions, protons,  hyperons and K0 s mesons, exhibit a
88
significant elliptic flow which grows both with the impact parameter and with the transverse
momentum. The increase of v2 as a function of pT is significantly weaker at SPS than at RHIC
energy. Pure hydrodynamic model calculations significantly overestimate NA49 semi-central v2 data
in contradiction to RHIC data which are reproduced by hydro predictions quite well.
179.
Resonance production in Heavy Ion Collisions at RHIC
what is strange and what is not so strange?
S.Vogel and M.Bleicher
Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität
Frankfurt am Main, D-60438 Germany, [email protected]
One of the most challenging observables in heavy ion collisions are resonance spectra, flow
patterns and yields. Since one can measure those particles only via their decay products the
experimental results depend strongly on the freeze-out mechanism and the surrounding medium.
Recent experimental data by the STAR collaboration suggests an ordering of cross sections of
resonance production in hot and dense nuclear matter. This phenomenon is investigated in a
hadron-string transport approach (UrQMD). Special emphasis will be put on strange baryon
resonances. It is found that the cross section ordering is directly related to regeneration and
rescattering effects of resonances in the hadronic medium and therefore to freeze-out times and radii.
This approach is ideal to probe the late stage of an heavy ion collision and is complimentary to HBT
analyses. Also the center of mass energies and regeneration probabilites of binary hadron hadron
reactions are investigated. It is observed that several resonances are much more likely regenerated
during a heavy ion collision than others. In the second part of the presentation elliptic flow patterns
of resonances will be investigated and compared to the spectra obtained by analyzing their decay
products. Correlations of both spectra are discussed and linked with v2 production in the early phase
of the heavy ion collision. Special emphasis will be put on RHIC energies.
180.
Elliptic flow fluctuations in 200 GeV Au+Au collisions at RHIC
Constantin LOIZIDESa for the PHOBOS Collaboration
Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
[email protected]
a
We will present the first results on event-by-event elliptic flow fluctuations in nucleus-nucleus
collisions, measured as a function of centrality with the PHOBOS detector. The measurement
crucially relies on the large pseudo-rapidity coverage of the PHOBOS multi-plicity array which
detects a very large fraction of the produced particles.
Our analysis procedure for extracting dynamical fluctuations consists of three major steps [1].
The elliptic flow (v2) is determined event-by-event by a maximum likelihood ¯t using its known
pseudo-rapidity dependence. For a given centrality bin, the detector response function is calculated
using detailed Monte Carlo simulations with varying input v2 values. The dynamical fluctuations are
determined by inverting the response function, which removes contributions of statistical
fluctuations and detector e®ects.
Our new data will improve the understanding of the connection between observed flow, the
initial geometry and the hydrodynamic evolution of the system. Studies from PHOBOS have
pointed out the importance of fluctuations in the initial-state geometry for understand-ing the large
Cu+Cu v2 value [2]. In a hydrodynamical scenario, such fluctuations in the shape of the initial
collision region would naturally lead to corresponding fluctuations in the elliptic flow signal.
Furthermore, it has been speculated that significant flow fluctuations could be generated by the
formation of topological clusters and development of filamentation instability [3]. Predictions of
these scenarios will be discussed in comparison to our data.
References：
[1] B. Alver for the PHOBOS collaboration, 2nd International Workshop on Correlations
89
and Fluctuations in Relativistic Nuclear Collisions, Proceedings of Science, 2006.
[2] S. Manly for the PHOBOS collaboration, 18th International Conference on NucleusNucleus Collisions, nucl-ex/0510031, 2005.
[3] S. Mrowczynski, E. Shuryak, Acta Phys. Polon. B34 (2003).
This work was partially supported by U.S. DOE grants DE-AC02-98CH10886, DE-FG02-93ER40802,
DE-FC02-94ER40818, DE-FG02-94ER40865, DE-FG02-99ER41099, and W-31-109-ENG-38, by U.S. NSF
grants 9603486, 0072204, and 0245011, by Polish KBN grant1-P03B-062-27(2004-2007), by NSC of Taiwan
Contract NSC 89-2112-M-008-024, and by Hungarian OTKA grant (F 049823).
181.
Two-particle angular correlations in pp, dA and AA collisions at PHOBOS
Wei Lia for the PHOBOS Collaboration
Department of Physics, Massachusetts Institute of Technology
Cambridge, MA 02139, USA, [email protected]
a
We will present our recent results on two-particle angular correlations in pp, dA and AA
collisions over a broad range of (  ,  ´) at RHIC. The study of particle correlations is of intense
interest and provides insight into the mechanism of multi-particle production in high energy
hadronic collisions. The PHOBOS detector at RHIC has a uniquely large coverage of the angular
distribution of charged particles, giving the opportunity to systematically explore the correlations
between particles at both short and long range pseudo-rapidity scales. We observe a complex 2D
correlation structure which we interpret in the context of the cluster model [1]. Quantitatively, the
cluster size and its decay width are extracted from the two- particle pseudo-rapidity correlation
function. Our results for pp collisions at 200 GeV and 410 GeV show good consistency with
previous measurements at ISR and SP¹PS [2], and provide more precise information on the energy
and multiplicity dependences of the clusters. Extending the analysis procedure to dA and AA
systems, we further study the system size dependence of the clusters which helps to probe the
hadronization of the hot and dense medium created in the heavy ion collisions.
Furthermore, the extracted cluster properties give important information for other anal-yses. This
includes elliptic flow and elliptic flow fluctuations, where the observed clusters contribute to
\non-flow" effects, and measurements of forward/backward multiplicity corre-lations.
This work was partially supported by U.S. DOE grants DE-AC02-98CH10886, DE-FG02-93ER40802,
DE-FC02-94ER40818, DE-FG02-94ER40865, DE-FG02-99ER41099, and W-31-109-ENG-38, by U.S. NSF
grants 9603486, 0072204, and 0245011, by Polish KBN grant 1-P03B-062-27(2004-2007), by NSC of Taiwan
Contract NSC 89-2112-M-008-024, and by Hungarian OTKA grant (F 049823).
References：
[1] E. L. Berger, Nucl. Phys. B 85, 61 (1975).
[2] UA5 Collaboration, Z. Phys. - Particle and Fields C 37, 191 (1988).
[3] B. B. Back et al., arXiv:nucl-ex/0603026.
182.
Methods for Jet Studies with Three-Particle Correlations
Claude A Pruneau
Physics and Astronomy Department,Wayne State University,
666 West Hancock,Detroit,MI 48152 USA. [email protected]
We present a method based on three-particle azimuthal correlation cumulants for the study of
the interaction of jets with the medium produced in heavy ion collisions at RHIC and LHC where
jets cannot be reconstructed on an event-by-event basis with conventional jet finding
algorithms.The method is specifically designed to distinguish a range of jet interaction mechanisms
such as Mach cone emission, gluon Cerenkov emission, jet scattering, and jet broadening. We
describe how anisotropic flow background contibutions of second order (e.g. v2 2 ) are suppressed in
three-particle azimuthal correlation cumulants, and discussed specific model representations of
di-jets, away-side scattering, and Mach cone emission.
183.
90
Two- and three particle azimuthal correlations of high-pt charged hadrons in
Pb-Au collisions at 158 AGeV beam energy.
S. Kniegea and M. Ploskona for the CERES collaboration
Institut für Kernphysik, Johann Wolfgang Goethe Universität Frankfurt am Main, Max-von-Laue-Str. 1,
60438 Frankfurt, Germany, [email protected], [email protected]
a
Azimuthal correlations of hadrons with high transverse momenta serve as a measure to study
the energy loss and the fragmentation pattern of jets emerging from hard parton-parton
interactions.Results from the CERES experiment on high-pt particle production and two particle
correlations in Pb-Au collisions will be presented for different centralities of the collisions.A study
of the correlations for different charge combinations of trigger and associate particles reveals charge
ordering in the fragmentation process and sensitivity of the correlation function to the type of the
leading hadron.Furthermore, a strongly non-Gaussian shape on the ”away-side” of the two particle
correlation function is observed in central collisions, indicating significant interactions of the
partons with the medium. Mechanisms like elastic scattering of the initial partons or the evolution
of a mach cone in the medium can lead to the same observed modification of the correlation
function on the ”away-side”. Different scenarios are discussed and an analysis based on
three-particle correlations is presented which helps to shed light on the origin of the observed
away-side pattern.
184.
Multiplicity fluctuations in Cu+Cu and Au+Au collisions at RHIC
aInstitute
K. Wo´zniaka for the PHOBOS Collaboration
of Nuclear Physics PAN Krakow, Poland, [email protected]
The event-by-event multiplicity of charged particles is measured by the PHOBOS experiment
for different energies and colliding nuclei with almost full pseudorapidity and azimuthal coverage.
This allows the study of fluctuations of both the total number of charged particles and their angular
distribution. Using the large Cu+Cu and Au+Au datasets of 500 M and 250 M events, respectively,
we present a new upper limit on the fraction of events with unusual properties allowed by the data.
Such events may be expected due to physics processes in the early stage of the dynamical evolution,
e.g. associated with the Color Glass Condensate, the formation of topological clusters or the
development of filamentation instabilities,all of which might lead to large-scale long-range
correlations in particle production.In addition, we will extend previously-shown PHOBOS
measurements on forward-backward multiplicity fluctuations and provide comparisons with the
expectations from a model assuming production of particles in correlated ”clusters”. Changes in the
cluster properties may reflect a modification of the processes by which hadrons are produced, e.g.
via a quark-gluon plasma.
This work was partially supported by U.S. DOE grants DE-AC02-98CH10886, DE-FG02-93ER40802,
DE-FC02-94ER40818, DE-FG02-94ER40865, DE-FG02-99ER41099, and W-31-109-ENG-38, by U.S. NSF
grants 9603486, 0072204, and 0245011, by Polish KBN grant1-P03B-062-27(2004-2007), by NSC of Taiwan
Contract NSC 89-2112-M-008-024, and by Hungarian OTKA grant (F 049823)
.
185.
AN INVERSION-ASYMMETRIC SOURCE FUNCTION
FOR HBT ANALYSIS IN RELATIVISTIC HEAVY ION COLLISIONS
Liu Lianshou and Shi Shusu
Institute of Particle Physics, Huazhong Normal University
Wuhan, Hubei, 430079, P. R. China, [email protected],ccnu.edu.cn
Analysis of two-particle correlation provides a tool for determining the spatio-temporal
characteristics of relativistic heavy ion collisions. It is usually referred to as HBT analysis,
following the pioneer work of Hanbury-Brown and Twiss. Assuming a special functional form for
the emitting-source, one can determine the source size experimentally through fitting the measured
two-particle
correlations.
Two-particle
correlation
function
can
be
expressed
91
as C ( P, q)  1   d 3 rS p (r ) q (r ) 2
where P and q are the total and relative momenta of the particle
2
pair, respectively. q (r ) is a weight factor, which takes care of the indistinguishability of identical
particles. SP (r) is the source function. In order to extract SP (r) from the measured correlation an
assumption has to be made on its functional form. A Gaussian form for SP (r) is usually used both
for the longitudinal (beam) direction and for the 2 transverse directions. This is reasonable and is
consistent with the axial symmetry of the system in case the coordinates in transverse plane is
chosen arbitrarily.
However, the present convention is to use the Pratt-Bertsch parametrization, where the
projection K of pair momentum P in the transverse plane is defined as the out direction and the 3-D
space is decomposed into longitudinal — xl, out — xo and side — xs. In such a coordinate system
there is a fixed vector K along xo, which violates the inversion symmetry, and so to use a symmetric
Gaussian along this direction is doubtful. We use a Monte Carlo generator to simulate the
spatio-temporal evolution of the system and got an almond-shape distribution in the xo-xs plane.
Projecting to xo, the distribution is asymmetric with respect to the inversion xo ! ¡xo. A 3-parameter
— N-B-a distribution is proposed to extrapolate from nearly symmetric (nearly Gaussian) to highly
asymmetric through varying the parameters. It is found that in the Monte Carlo model we used the
asymmetry degree Ao, which vanishes for symmetric and equals unity for maximum asymmetric
distributions, varies with time from » 0:43 at t = 6 fm to » 0 33 at t = 27 fm.
It is suggested to use the proposed NBa distribution for xo together with Gaussian for xs and xl to fit
the experimentally measured correlation function. From the resulting parameters N, B and a the
asymmetry degree of the source along xo can be extracted. It is found that fitting a correlation
function using an asymmetric NBa source function the resulting source size R is bigger than the
result using Gaussian source. This means that the Ro=Rs ratio will become larger using
NBa+Gaussian than using 3-D Gaussian. This may help in understanding the Ro=Rs ratio puzzle.
186.
DETECTING QGP WITH CHARGE TRANSFER FLUCTUATIONS
S. Jeona;c, L. Shia, and M. Bleicherb
of Physics, McGill University, Montreal, Quebec, H3A-2T8, CANADA,
[email protected] b
bInstitut für Theoretische Physik, Johann Wolfgang Goethe Universitär
Robert Mayer Str. 8-10, 60054 Frankfurt am Main, Germany
cThe presenting author.
In this talk, the charge transfer fluctuation which was previously used for pp collisions is
proposed for relativistic heavy-ion collisions as a QGP probe.As the charge transfer fluctuation is a
measure of the local charge correlation length,it is capable of detecting inhomogeneity in the hot
and dense matter created by heavy ion collisions.Within a two-component neutral cluster model, we
demonstrate that the charge transfer fluctuation can detect the presence of a QGP as well as the size
of the QGP in the rapidity space.
Further, we show that the previously proposed net charge fluctuation is sensitive to the
existence of the second phase only if the QGP phase occupies a large portion of the available
rapidity space. We predict that going from peripheral to central collisions, the charge transfer
fluctuations at midrapidity should decrease substantially while the charge transfer fluctuations at the
edges of the observation window should decrease by a small amount. These are consequences of
having a strongly inhomogeneous matter where the QGP component is concentrated around
midrapidity. We also show how to constrain the values of the charge correlations lengths in both the
hadronic phase and the QGP phase using the charge transfer fluctuations.
References：
[1] S. Jeon, L. Shi and M. Bleicher,
187.
New Observable Predictions from Elastic, Inelastic, and Path Length Fluctuating Energy Loss
92
W. A. Horowitza, S. Wicksb, and M. Gyulassyc
of Physics, 538 West 120th Street, Columbia University, New York, NY, 10027, USA,
[email protected]
b
[email protected]; [email protected]
Using the extended DGLV radiative energy loss formalism convolved with elastic energy loss
in a realistically modeled medium, I show that the current high precision experimental  0 RAA data
is not a fragile tomographic probe of the medium produced at RHIC. A variety of new predictions is
presented that demonstrate robustness in the theoretical model and differentiate it from alternate
models of jet quenching. Results for RAA(pT ;  ), and hence v2(pT ), as well as back-to-back
correlations for all centrality classes measured at RHIC and the LHC will be shown. Systematic
errors stemming from incomplete knowledge of the elastic energy loss mechanism and the
imperfect treatment of overquenched partons will be reported.
188.
Charge fluctuations and signals of QGP phase transition
Dai-mei Zhoua and Ben-hao Sab
of Particle Physics, Huazhong Normal University Wuhan, Hubei, 430079, P. R. China,
[email protected]
bChina Institute of Atomic Energy P. O. Box 275 (18), Beijing, 102413 [email protected]
aInstitute
in both the partonic and hadronic stages of Au + Au collisions at top RHIC energy. Net charge
transfer fluctuation and the forward-backward charge fluctuation are calculated in the pure hadronic
scenario, the pure partonic scenario, and the scenario of final hadronic state developed from initial
partonic stage for Au+Au collisions. The corresponding results are symboled, respectively,
by”HM”,”QGM”, and”HM v. QGM” (here”v.” means via).We have determined the factor, κ, which
characterizes the net charge transfer fluctuation and the factor, σc2, which characterizes the
forward-backward charge fluctuations. Considering pure hadronic and pure partonic scenario, we
obtain a factor of 3-5 difference in κ. However, switching on the hadronization of the parton matter
and introducing secondary hadron-hadron interactions, the factor κ will be increasing and
approaching the value of the pure hadronic scenario within a 20 %. As for the forward-backward
charge fluctuation, σc2 decreases gradually form”QGM”, to”HM v. QGM”,and then to”HM” both
in central and semi-peripheral Au+Au collisions.
References
[1] Ben-Hao Sa, Dai-Mei Zhou, and Zhi-Guang Tan, J. Phys. G , v. 32, p. 243-250,2006.
[2] Dai-Mei Zhou, Xiao-Mei Li, Bao-Guo Dong, and Ben-Hao Sa, Phys. Lett. B, v. 638,p. 461-463, 2006.
189.
V. Beguna and M. Gorensteina
Institute for Theoretical Physics,
14-b, Metrolohichna str., Kiev, 03680, Ukraine, [email protected]
aBogolyubov
The charged hadron multiplicity fluctuations are considered in the canonical ensemble. The
microscopic correlator method is extended to include three conserved charges: baryon number,
electric charge and strangeness. The analytical formulae are presented that allow to include
resonance decay contributions to correlations and fluctuations. We make the predictions for the
scaled variances of negative, positive and all charged hadrons in the most central Pb+Pb (Au+Au)
collisions for different collision energies from SIS and AGS to SPS
and RHIC.
References：
[1] V. V. Begun, M. I. Gorenstein, M. Hauer, V. P. Konchakovski and O. S. Zozulya,
arXiv:nucl-th/0606036, submitted to Phys.Rev.C.
190.
93
New results on pion-pion and pion-proton correlations from
the CERES Pb+Au run at 158 GeV per nucleon
D. Antończyka and D. Miśkowieca for the CERES Collaboration
Gesellschaft für Schwerionenforschung
Darmstadt, 64291, Germany, [email protected], [email protected]
a
We present a recent analysis of the fully calibrated high statistics CERES Pb+Au collision data
at the top SPS energy, with the emphasis on the pion-proton correlations and the event-plane
dependence of the HBT radii. The pion-proton correlations, analyzed in two dimensions of the
relative momentum allow one to study how the clearly visible displacement between the source of
pions and protons evolves with the pair p⊥ Derived results lend support to a transverse expansion
picture consistent with the one deduced from the pion-pion HBT radii and offer an independent
cross-check of flow measurements in heavy-ion collisions. The transverse momentum and the
event-plane dependence of the pion correlation radii are discussed together with the transverse
momentum spectrum and the elliptic flow in the framework of the blast wave model of the
expanding fireball.
191.
Measuring Shear Viscosity Using Transverse Momentum Correlations
S. Gavina and M. Abdel-Azizb
of Physics and Astronomy, Wayne State University, Detroit, MI, USA
bInstitut für Theoretische Physik, J.W. Goethe UniversitÄat, Frankfurt am Main, Germany
Elliptic flow measurements at RHIC suggest that quark gluon plasma flows with very little
viscosity compared to weak coupling expectations, challenging theorists to explain why this fluid is
so nearly \perfect". It is therefore vital to find quantitative experimental information on the viscosity
of the plasma. We propose that transverse momentum correlation measure-ments can be used to
extract information on the kinematic viscosity, v   / Ts , where  is the shear viscosity, s is the
entropy density and T is the temperature. This ratio characterizes the strength of the viscous force
relative to the °uid's inertia and, consequently, determines the effect of  on the flow. We argue
that viscous diffusion broadens the rapidity dependence of transverse momentum correlations, and
then show how these correlations can be extracted from measurements of event-by-event pt
fluctuations. We then use current data [1] to estimate the viscosity-to-entropy ratio in the range
from 0.08 to 0.3, and discuss howfuture measurements can reduce this uncertainty [2].
References：
[1] J. Adams et al. [STAR Collaboration], arXiv:nucl-ex/0509030.
[2] S. Gavin and M. Abdel-Aziz, arXiv:nucl-th/0606061.
192.
PARAMETRIZATION OF BOSE-EINSTEIN CORRELATIONS
AND RECONSTRUCTION OF THE SOURCE FUNCTION
USING THE L3 DETECTOR
T. Nováka, T. Csörgöa;b, W.J. Metzgera, W. Kittela
representing the L3 Collaboration
aRadboud University, 6525ED Nijmegen, The Netherlands, [email protected]
bVisitor from Budapest, Hungary, sponsored by the Scientific Exchange between Hungary (OTKA)
and The Netherlands (NWO), project B64-27/N25186.
In comparison to heavy ion collisions, Bose-Einstein correlations of identical charged-pion
pairs produced in hadronic Z decays are analyzed in terms of various parametrizations. A good
description is achieved using a Lévy stable distribution in conjunction with a hadronization model
having highly correlated configuration and momentum space, the  -model. Using these results, the
source function is reconstructed and compared to that in hadron-hadron and heavy-ion collisions.
193.
94
ECCENTRICITY FLUCTUATIONS AND ELLIPTIC FLOW AT RHIC
Rajeev S. Bhaleraoa and Jean-Yves Ollitraultb
Department of Theoretical Physics, TIFR
Homi Bhabha Road, Colaba, Mumbai 400 005, India, [email protected]
b
Service de Physique Théorique, CEA/DSM/SPhT, Unité de recherche associée au CNRS
F-91191 Gif-sur-Yvette Cedex, France, [email protected]
a
Elliptic flow, v2, is one of the most important observables in nucleus-nucleus collisions at
RHIC. Preliminary analyses of v2 in Cu-Cu collisions at RHIC, presented at the QM'2005
conference, reported values surprisingly large compared to theoretical expectations, almost as large
as in Au-Au collisions. It was shown by the PHOBOS collaboration that fluctuations in nucleon
positions provide a natural explanation for this large magnitude [1].Fluctuations in the nucleon
positions result in °uctuations in the almond shape and orientation of the overlap zone in
nucleus-nucleus collisions, which can affect its spatial eccentricity ε.In this work, we discuss
various definitions of the eccentricity of the overlap zone. We show that estimates of v2 using
different methods (namely, the standard event-plane method, the event-plane method using directed
flow in a zero-degree calorimeter, 4-particle cumulants) should be scaled by appropriate choices of
the eccentricity [2].We also compute the e®ect of °uctuations on the eccentricity semi-analytically
to leading order in 1=N, where N is the mean number of participants at a given centrality. We show
that when v2 is analyzed from 4-particle cumulants, or using the event plane from directed flow in a
zero-degree calorimeter, the result is insensitive to eccentricity fluctuations. We find that
the °uctuations in the eccentricity dominate over fluctuations in size and density of the overlap
zone.Numerical results for the various eccentricities as a function of the number of participant
nucleons will be presented for Au-Au and Cu-Cu collisions at RHIC.
References：
[1] S. Manly et al., [PHOBOS Collaboration], nucl-ex/0510031.
[2] R.S. Bhalerao and J.-Y. Ollitrault, nucl-th/0607009.
194.
Particle production and correlation in ep collisions
on behalf of the H1 and ZEUS collaborationsa
The speaker will be nominated from the H1 or ZEUS collaborations
after the talk is confirmed.
The contact person for this talk is: Yuji Yamazaki, KEK
currently at DESY, Notkestr. 85, 22607 Hamburg, Germany,
[email protected]
Electron-proton collisions at HERA can be regarded as an interaction between a virtual photon
and the proton. The interaction gives a unique opportunity for studying particle production as well
as it bridges two other high-energy collider environments, namely $e^+e^-$ collisions, where the
on particle production in the hadronic final state of the $ep$ collisions, with an emphasis on strange
meson and baryon production. The Bose-Einstein correlation length was also measured. The results
are compared to the results from other colliders.
195.
Energy-Energy Correlations and Other Di-Jet/Jet-Photon Correlations in PHENIX
Justin Frantz
Department of Physics, SUNY Stony Brook,
Stony Brook, NY, 11794, USA, [email protected]
An integral part of the RHIC program has been to use jet probes to study the Heavy Ion
Medium. Such measurements have progressed from comparisons of plain particle yields at high pt,
to two-particle opening angle correlations, and currently further jet observables are being explored.
As a new twist and point of view on the interesting pt-dependence of the di-jet azimuthal
correlations, we have explored the Energy-Energy Correlation (EEC) in both 200 GeV Au+Au
(run4 dataset) and p+p collisions which represents the autocorrelation of the energy flow, as
95
opposed to the multiplicity flow, of the jet fragmentation. Such measurements are attractive since
they require no jet-finding in Au+Au but are a step towards event shape observables used to study
perturbative and non-perturbative QCD. The starting point is to make the measurement in p+p using
the run5 dataset for comparison which would be a first for h+h, at least at these scattering energies.
We've explored a technique for measuring the EEC using photon-triggered events and thus we will
also present results related to the PHENIX direct photon-jet measurements.
196.
GLUON TRANSVERSE MOMENTA AND HEAVY QUARK-ANTIQUARK
PAIR PRODUCTION AND CORRELATONS IN HADRONIC
COLLISIONS AT HIGH ENERGY
A. Szczureka b and M. L
ￃ uszczakb
a
Institute of Nuclear Physics PL-31-342 Cracow, Poland, [email protected]
b
University of Rzeszów PL-35-959 Rzeszów, Poland
We discuss and compare different approaches to include gluon transverse momenta for heavy
quark-antiquark pair production. The correlations in azimuthal angle and in heavy quark, heavy
antiquark transverse momenta are studied in detail. The results are illustrated with the help of
different unintegrated gluon distribution functons (UGDF) from the literature. We compare results
obtained with on-shell and off-shell matrix elements and kinematics and quantify where this effects
are negligible and where they are essential. We concentrate on the region of asymmetric transverse
momenta of charm quark and charm antiquark. Most of UGDFs lead in this corner of the phase
space to almost full decorellation in azimuthal angle. We propose correlation observables to be best
suited in order to test the existing models of UGDFs.Kinematical correlations for b  b are
studied.The inclusive cross section for D¤ and B+ mesons are calculated in the formalism of
UGDFand the results are compared with experimental data.This presentation is partially based on
the paper [1].
References：
[1] M. ÃLuszczak and A. Szczurek, Phys. Rev. D73 (2006) 054028.
197.
A METHOD FOR MEASURING ELLIPTIC FLOW FLUCTUATIONS
WITH 1ST-ORDER EVENT PLANES
A.H. Tanga, G. Wangb and S.A. Voloshinc
National Laboratory, Upton, New York 11973 USA, [email protected]
bUniversity of California, Los Angeles, California 90095, USA [email protected]
cWayne State University, Detroit, Michigan 48201, USA, [email protected]
aBrookhaven
Elliptic flow v2 carries information on the early stage of high-energy heavy-ion collisions, and
has been extensively studied. Event-by-event fluctuations of v2 have long been people's goal of
measurement, yet not thoroughly studied because most methods involve 2nd-order event planes that
are influenced by v2 fluctuations in the first place. We present a new method for measuring
event-by-event fluctuations of v2 with 1st-order event planes. By studying the event-by-event
distributions of v2 observables and 1st-order event-plane observables, we can not only measure v2
directly, but also separate the real v2 fluctuation from other fluctuation effects such as multiplcity
fluctuation. Corrections for the detector inefficiency are also discussed in this method. The method
has been tested with Monte Carlo simulations. In practice, this method is feasible for the current
experiments such as STAR at RHIC, where the 1st-order event planes can be obtained via either
forward Time Projection Chambers or Shower Maximum Detectors at Zero Degree Calorimeters.
With 1st-order event planes thus obtained, nonow effects, another source of systematic errors of v2
measurement, will also be greatly suppressed. The new method may also benefit the heavy ion
experiments at LHC in a similiar way.
198.
Two- and Three-particle Correlations in a Partonic Transport Model
96
G. L. Maa, Y. G. Maa , S. Zhanga;b, X. Z. Caia,
J. H. Chena, H. Z. Huangb, W. Q. Shena
a
Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
b
University of California, Los Angeles,CA90095, USA
emails: [email protected] or [email protected]
A Mach-like structure has recently been observed in experimental researches of di-hadron and
three-particle correlations at RHIC [1], for which several interpretations have been proposed. One
interpretation is that a Mach shockwave has been produced when the velocity of jet is faster than
the speed of sound in dense QCD medium. Alternative explanation of Mach-like structure by QCD
Cherenkov radiation mechanism has also been proposed. We will use a multi-phase transport model
scatterings in Au+Au collisions at Sqrt(Snn)=200 GeV. We found that the parton cascade
mechanism is essential for Mach-like structure, i.e. the Mach-like is mostly born in parton cascade
process in the early stage and continues to develop in the hadronic phase [2]. We will present the
time evolution of Mach-like structure in the parton transport process. Quantitatively, the AMPT
model with the string melting scenario, which includes the parton cascade mechanism, gives a
splitting parameter of the Mach-like angles increasing slowly with the transverse momentum of
associated hadrons. This dependence is consistent with preliminary experimental observations [3],
but different from the predictions of hydrodynamics and Cherenkov radiation. Implications on the
dynamics for the Mach-like structure will be discussed and additional experimental tests will be
suggested.
References:
[1] S. S. Adler et al. [PHENIX Collaboration], arXiv:nucl-ex/0507004; J. G. Ulery [STAR Collaboration],
arXiv:nucl-ex/0510055.
[2]G. L. Ma, S. Zhang and Y. G. Ma et al. arXiv:nucl-th/0601012.
[3]Mark J. Horner [STAR Collaboration] arXiv: nucl-ex/0606025.
199.
TWO-PARTICLE CORRELATION IN HEAVY-ION COLLISIONS AT CSR ENERGY
J. B. Zhanga
of Physics, Harbin Institute of Technology,
Harbin, 150001, P. R. China, [email protected]
a Department
The predictions of the two-particle correlation by using the Relativistic Quantum Molecular
Dynamics (RQMD) model are presented for the heavy-ion reactions at HIRFL-CSR energies. The
n-n, p-p and p-n correlation functions with the final state interaction are calculated with the
Lednicky code for the C+C collisions at 1.1 AGeV and U+U at 520 AMeV respectively. he
relationship between the freeze-out spatial distributions and the parameters of correlation
femtopscopy is investigated. We find that one can reliably reconstruct the source functions from
the two-particle correlation functions with ignoring the degree of space-momentum correlations.
The results are also comparing to the Bevalac EoS experimental data at the same energy region.
References:
[1] M. A. Lisa, S. Pratt, R. Soltz and U. Wiedemann, Annual Review of Nuclear and Particle Science , v. 55, p.
357-402, 2005.
200.
PROTON FEMTOSCOPY IN STAR
a
b
Hanna Paulina Gosa,b
Faculty of Physics, Warsaw University of Technology,Warsaw, 00-662, Poland, [email protected]
Subatech, Ecole des Mines de Nantes, CNRS/IN2P3, Universite de Nantes, Nantes, France.
Two particle femtoscopy is a powerful tool for the investigation of the properties of the matter
produced in heavy ion collisions at ultra-relativistic energies. Applied to the identical and
nonidentical pairs composed of protons and anti-protons it allows for the study of the space-time
properties of the baryon sources.
The ratio of anti-proton to proton multiplicities is still less than one at RHIC energies, and the
97
masses of baryons are larger with the respect to pions and kaons. Futhermore, the differences in the
scattering cross sections, and the production of resonances can create dif- ferences between
space-time properties of baryon and meson emission in heavy ion collisions. Information about
these characteristics of particle emission is especially important as the complex processes of
collective and thermal motions, the rescattering of secondary particles, and production of
resonances determine the behaviour of nuclear matter at the final stage of the collision. Baryon and
anti-baryon source sizes extracted from baryon-baryon interferometry com- plement the
information deduced from the correlation studies of identical pions. The collec- tive behaviour of
the source is revealed through mT dependence of HBT radii for different particle species. We focus
on whether the proton source sizes scale as predicted by flow or multiplicity with respect to the
measured pion source sizes. For the first time the large statistics collected by STAR enable the
extraction of both proton and anti-proton source sizes for three centralities and two different
energies: √sNN = 62.4 and 200 AGeV.
Due to a wide and pronounced correlation effect the proton-anti-proton correlation function
shows better sensitivity to the source size than the one for identical protons. The source sizes
deduced from the identical baryon combinations supplement those obtained from noniden- tical
system, thus constructing a consistent picture of the source emitting baryons. Futhermore, the
proton-anti-proton correlation allows for a check of the validity of the expectation that protons and
anti-protons are emitted on the average at the same space-time position as predicted in a
hydrodynamical prediction. Due to the nonidentical particle correlation method we are able to
detect the presence of any asymmetry in the emission process be- tween proton and anti-protons.
We account for the residual correlations induced by Λ and Σ feeddown by introducing a new
correction method that we have developed, the results from which we compare with theoretical
predictions. Thus, we are able to gain new insight into the baryon production and the interaction
mechanisms due to the large statistics available in STAR.
201.
Methods for Measuring Elliptic Flow Fluctuations
P. Sorensena and S. Voloshinb
Department, Brookhaven National Laboratory,Upton, NY, 11973, USA, [email protected]
bDepartment of Physics and Astronomy, Wayne State University
666 W. Hancock Street, Detroit, MI 48201, [email protected]
aPhysics
We present new methods for measuring event-to-event fluctuations of elliptic flow v2. Since
v2 is sensitive to the initial stages of heavy-ion collisions, it has been studied extensively by
experiments at the AGS, SPS, and RHIC facilities. Fluctuations of v 2 from event-to-event,
however, have not yet been presented. v2 fluctuations are potentially sensitivity to critical point
fluctuations and may help to distinguish between different models of initial conditions in heavy-ion
collisions. Also, for determining unbiased v2 values, removing effects due to fluctuations is as
important as removing non-flow correlations. Precise comparisons to theoretical calculations are
therefore only possible if both non-flow correlations and v2 fluctuations are understood. We present
new methods, and critically review previously proposed methods of measuring v2 fluctuations.
Simulations are carried out to demonstrate the effectiveness of using the flow-vector length for
simultaneously measuring mean v2 and fluctuations of v2 in low multiplicity events and in the
presence of non-flow correlations and higher order anisotropy v4.
202.
Azimuthal Correlations in sNN = 200 GeV Au+Au and Cu+Cu Collisions
Jiamin Jin, for the PHENIX COLLABORATION
Department of Physics, Columbia University New York, New York, 10027, USA,
[email protected]
The method of high pT two particle azimuthal correlations is a unique probe of the hot dense
98
medium created in heavy-ion collisions at RHIC.Early RHIC results on hadron-hadron correlations
indicate a strong modification of the away side jet shape and yield by the medium. These
modifications provide valuable constraints on the properties of the hot dense medium. However, the
physics interpretations of the away side modification are complicated because the triggering jets are
modified as well. Direct photons, due to their weak coupling with the medium, provide a cleaner
calibration of the energy and direction of the away side jets. Thus, direct photon-hadron correlations
can provide less biased and quantitative measurements of the away side modifications.
At RHIC energies, identification of direct photons is difficult due to the large contamination
from hadronic decays, mostly from neutral pions. Thus the extraction of the direct photon-hadron
correlation signal relies on a statistical subtraction of the decay photon-hadron from inclusive
photon-hadron correlations. We present our latest results on the high pT (>5GeV/c) π0-hadron and
inclusive photon-hadron correlations in Au+Au and Cu+Cu collisions at sNN =200GeV. Both the
shape and the yield of the near/away side jets will be studied as a function of centrality and
associated hadron pT. The same information is also measured in p+p collisions to quantify the
modification of jet fragmentation via comparisons of xE and other yield distributions. We also show
our latest results on extracting the direct photon-hadron correlations and yields via the statistical
subtraction method. Its implication on the jet quenching pictures will be discussed.
203.
Probing the nature of the long-range structure observed in the pion emission source at
RHIC-PHENIX
Paul Chunga for the PHENIX collaboration
of Chemistry, SUNY Stony Brook Stony Brook, New York, 11794, USA,
[email protected]
A deconfined phase of nuclear matter is expected to be formed at the high energy densities
created in relativistic heavy ion collisions. It is widely believed that important signatures for the
formation of such a phase are reflected in the space-time extent and the shape of particle emission
source functions.
Recently, 1-Dimensional source imaging techniques have revealed a non-trivial long range
structure in the two-pion emission source at RHIC energies. In order to determine the origins of this
long range structure, it is necessary to carry out a 3-Dimensional source imaging analysis of the
pion emission source shape, possibly for several different transverse momentum (kT) values of the
pion pairs and colliding systems.
The PHENIX Collaboration at RHIC has acquired ∼ 1.5 billion Au+Au events at
sNN =200GeV during the year-2004. This large data set allows for the extraction of the
3-Dimensional shapes for pion emission sources as a function of transverse momentum with very
high resolution. These 3-Dimensional source images will be discussed in the context of Gaussian
shape assumption and compared with model calculations in order to assess the role of resonances.
Also, the latest status of 3D pion source images from Cu+Cu events at sNN =200GeV will be
reported.
204.
Suppression of Statistical Background in Event-Structure Analysis Using Factorial Moments
C.B. Chiua and R.C. Hwab
for Particle Physics and Department of Physics, University of Texas at Austin Austin, TX 78712,
USA, [email protected]
bInstitute of Theoretical Science and Department of Physics, University of Oregon Eugene, OR
97403-5203, USA, [email protected]
aCenter
In the study of event structure of jet production in heavy-ion collisions the conventional
approach is to subtract the background after summing over all events. It is meaningless to
make background subtraction event by event. However, summing over all events is a process
99
in analysis that often degrades the signal. To enhance the signature we propose a measure
based on factorial moments that largely filter out the statistical fluctuation in every event. The
factorial moments are sensitive to the jet characteristics without the necessity of background
subtraction. We have applied the method successfully to the analysis of azimuthal distribution
of events triggered by high pT particles. Asymmetry moments can well separate one-jet and
two-jet recoil scenarios. Application of this method to the analysis of the RHIC data on jet
correlation may provide a common framework to compare results from widely different
experimental conditions and various subtraction schemes.
205.
Understanding the Particle Production Mechanism with Correlation Studies Using Long and
Short Range Correlations and the Balance Function.
Brijesh Srivastava for the STAR Collaboration
Purdue University, [email protected]
The study of correlations among particles produced in different rapidity regions may provide an
understanding of particle production mechanisms. Production of particles in the central rapidity
region is dominated at all energies by short range correlations. Correlations that extend over a
longer range are observed in hadron-hadron interactions only at higher energies. The rapidity
correlations between oppositely charged particles, the so called balnce function has also been
proposed as a measure of the hadronization time. Results for short and long-range multiplicity
correlations (forward-backward) are presented for Au+Au collisions at sNN = 200 GeV. These
correlations are measured with increasing values of a gap in pseudorapidity, from no gap at
midrapidity to a separation of 1.6 units (+/- 0.8). A suppression in the correlation strength near
midrapidity is observed in central Au+Au data at sNN = 200 GeV, along with an increase in
long-range correlations with larger rapidity gaps. This pattern is seen only for low transverse
momentum pt particles, pt < 1 GeV. For pt > 1 GeV, the suppression in short range correlations is
diminished. This result may indicate a reduction in number of particle sources for central Au+Au
collisions at sNN = 200 GeV and the possible formation of high density matter. Both string
fusion/percolation and color glass condensate can explain the long range correlations observed in
data. The balance function (BF) has been measured for identified charged pions and kaons. BF for
identified charged pions narrow in central collisions while the BF for charged kaons show no
centrality dependence. This difference may indicate that pions and kaons are created at different
times. The results from the pseudorapidity, centrality and transverse momentum dependence of BF
are also presented.
206.
Net charge fluctuations using higher order cumulants
Tapan K. Nayaka,b for the STAR Collaboration
Energy Cyclotron Center1/AF Bidhan Nagar, Kolkata - 700064, India;
[email protected]
bPresent Address: CERN, CH-1211, Geneva-23, Switzerland
aVariable
We present the study of net-charge fluctuations in p–p, d–Au, Cu–Cu and Au–Au collisions at
RHIC energies as measured by the STAR experiment using higher order cumulants. Fluctuations of
conserved quantities like net electric charge, baryon number and strangeness are predicted to be
significantly reduced in a QGP scenario as they are generated in the early plasma stage of the
system created in heavy-ion collisions with quark and gluon degrees of freedom [1,2].
Fluctuations of net electric charge have recently been calculated using lattice QCD framework [3,4].
These calculations have shown that the ratio of the second to fourth order cumulants of the net
charge distribution reflects the relevant degrees of freedom which carry the electric charge. In the
hadronic phase this ratio has an increase with increasing temperature up to the critical temperature,
TC, and a rapid suppression is seen in the high temperature phase of QGP.
100
Net charge fluctuations have been measured by experiments at SPS and at RHIC using
different fluctuation measures constructed from the mean and variance of the distributions. The
fluctuations, measured by the the STAR experiment [5], are in qualitative agreement with resonance
gas and quark coalescence models. For the first time we will present results from higher order
moments. The ratio of the second to fourth order moments, expressed in terms of kurtosis, is a measure the deviation from a normal distribution in terms of its peakiness (positive kurtosis) or flatness
(negative kurtosis) at the mean. The kurtosis for most peripheral Cu–Cu and Au–Au collisions are
similar to those of the p–p collisions, implying that pair production is the dominant mechanism of
charged particle production for p–p as well as most peripheral heavy-ion collisions. The kurtosis
values decrease with increasing centrality and are close to zero for central Cu–Cu and Au–Au
collisions. Comparison of these results with the lattice calculations will be made.
References
[1] S. Jeon and V. Koch, Phys. Rev. Lett. 85 (2000) 2076.
[2] M. Asakawa, U. Heinz, B.Muller, Phys. Rev. Lett. 85 (2000) 2072.
[3] S. Ejiri, F. Karsch, and K. Redlich, Physics Letters, B633 (2006) 275.
[4] R.V. Gavai, and Sourendu Gupta, Physical Review D72 (2005) 054006.
[5] C. Pruneau et al. (STAR Collaboration), talk at the Quark Matter 2005 conference, Budapest.
207.
What do PHENIX measurements of jet mediated identified particle correlations tell us about
the sQGP at RHIC?
W. G. Holzmanna (for the PHENIX Collaboration)
of Chemistry, Stony Brook UniversityStony Brook, NY, 11794-3400, U.S.A.,
[email protected]
Azimuthal angular correlation measurements provide an indispensible probe for the properties
of the novel partonic matter created in A+A collisions at RHIC [1]. These correlations have been
reliably decomposed into a jet mediated component and an underlying event [2]. Analyses of the jet
component suggest strong modifications to jet yields and topologies for unidentified charged
hadrons [3]. Full use of this short wavelength tomographic probe of the medium undoubtedly
depends on detailed angular correlation measurements for identified jet fragments. In particular, the
distinction between several competing mechanistic conjectures for jet modification hinges on the
unique insight into jet fragmentation offered by identified particle correlations. The PHENIX
experiment at RHIC has recently made detailed systematic measurements of jet induced
multi-particle correlations for several trigger and associated particle species combinations in
Au+Au collisions at sNN = 200GeV; they indicate strong species dependent modifications of the
away-side jet. The status of these measurements will be given along with their implications for the
hot and dense QCD matter produced in RHIC collisions.
References
[1] P. Jacobs and X.-N. Wang, Prog.Part.Nucl.Phys. 54 (2005) 443-534 and references therein
[2] N. N. Ajitanand et al, Phys.Rev. C72 (2005) 011902
[3] S. S. Adler et al, Phys. Rev. Lett. 97, 052301 (2006)
208.
Identification of Mach-Cone Using Three-Particle Jet-Like Correlations
aPurdue
Jason Glyndwr Ulerya
University, West Lafayette, Indiana 47907, USA, [email protected]
Two-particle correlations are significantly broadened on the away side in central Au+Au
collisions at RHIC. Conical flow, due to Mach-cone shock-waves generated by disturbances in the
created hydrodynamic medium by partonic energy loss, was proposed to explain this observation
[1-3]. However, ambiguity exists as the 2-particle observation is also consistent with other physical
scenarios, including QCD Cerenkov radiation [4], large angle gluon radiation, jet deflection by
transverse flow and path-length dependent energy loss.
Such ambiguity is lifted in 3-particle correlation and its pT dependence. Recent 3-particle
101
correlation data from STAR [5] show distinctive features of conical emission from Mach- cone
and/or Cenrenkov radiation. The analysis followed the commonly used jet-correlation method,
extended to three particles. Combinatoric backgrounds are obtained from mixed-events technique;
they include background from three random particles (with anisopotic flow) as well as background
from two correlated particles with a random one. The analysis procedure and systematic effects will
be discussed in detail.
Recently, other analysis methods have been proposed, including the 3-particle cumulant
method [6] and the polar-coordinate system method [7]. We show analytically and through Monte
Carlo that the cumulant method yields results that are obscured by structures introduced by its
background subtraction scheme. Given the measured 2-particle correlation strength and shape [8,9],
we demonstrate using Monte Carlo that the cumulant method cannot observe the Mach-cone signal.
The polar-coordinate method would be superior in identifying conical emission if the away-side
jet axis is known. However, without that knowledge the results become complicated, as will be
shown by Monte Carlo simulation. We propose to remedy this by using 4-particle correlations with
a second leading particle opposite to the trigger particle, and analyzing the two softer particles in
the polar-coordinate system around the direction of the away-side second leading particle. We
demonstrate its potential with Monte Carlo and argue that the STAR experiment is well suited for
such an analysis.
References:
[1] H. Stoecker, Nucl. Phys. A750, 121 (2005), nucl-th/0406018.
[2] J. Casalderrey-Solana, E.V. Shuryak, and D. Teaney, hep-ph/0411315.
[3] J. Ruppert and B. Muller, Phys. Lett. B618, 123 (2005), hep-ph/0503158.
[4] V. Koch, A. Majumder, and X.-N. Wang, Phys. Rev. Lett. 96, 172302 (2006).
[5] J. Ulery (STAR), talk given at Hard Probes 2006.
[6] C. Pruneau, nucl-ex/0608002.
[7] N. Ajitanand (PHENIX), talk given at Hard Probes 2006.
[8] S.S. Adler et al (PHENIX), Phys. Rev. Lett. 97, 052301 (2006), nucl-ex/0507004.
[9] J.G. Ulery (STAR), nucl-ex/0510055.
209.
Search for a critical behavior by measuring spatial correlation lengths via multiplicity density
fluctuations at RHIC-PHENIX
Kensuke Homma for the PHENIX collaboration
Div. Astro-&Particle-Physics, Physical Science, Graduate School of Science, Hiroshima Univ. 1-3-1
Kagamiyama, Higashi-hiroshima 739-8526, Japan
RHIC experiments have probed the state of strongly interacting dense medium with proper- ties
consistent with partonic pictures. However, information on the phase transition has not been
quantified yet. Where is the critical point? What is the transition order? Based on the
Ginzburg-Landau free energy with a spatially inhomogeneous term as a function of a scalar order
parameter, it is possible to determine spatial correlation lengths from measured two point
correlation functions where a multiplicity fluctuations from the mean value is taken as the scalar
order parameter. In the vicinity of critical temperature, the correlation length is expected to diverge
in general. In this talk, results from the PHENIX experiment in Au+Au collisions at sNN =
200GeV will be presented, where we will focus whether critical behaviors of phase transitions exist
or not by searching for increase patterns of correlation lengths as a function of energy density. In
addition latest status in Au+Au at 62.4GeV and Cu+Cu at 62.4 and 200GeV will be presented.
210.
mT and centrality scaling properties of source size and duration time measured by
Bose-Einstein correlations at RHIC-PHENIX
A. Enokizonoa for the PHENIX Collaboration
Livermore National Laboratory 7000 East Ave., Livermore, California 94550, USA,
[email protected]
aLawrence
The Bose-Einstein correlation (aka HBT) measurements of hadrons provide the information of
102
the source extent and duration time (HBT radii) of the hot and dense hadronic matter created in
relativistic heavy-ion collisions. With extensive measurements from AGS to RHIC energies over
the last decades, the HBT radii of charged pions have been found to be un- expectedly small and
less changed from AGS to RHIC energies beyond naive expectations in the first-order phase
transition and calculations by hydrodynamics models. Detailed systematic studies of HBT radii for
different particles, colliding beam energies and species are expected to give more insights in the
freeze-out dynamics of hadrons at RHIC.
We present PHENIX-HBT measurements of charged pion, kaon and proton in Au+Au
collisions at sNN = 200GeV and systematically investigate the pair momentum and centrality
dependences of 3-D HBT radii. The HBT radii are measured in a conventional Gaussian
assumption and side-out-long (aka Bertsch-Pratt) parameterization. Also the latest status of the
HBT analyses of charged pion in Au+Au, Cu+Cu and p+p at sNN = 63 and 200GeV is presented
and scaling properties of HBT radii in terms of colliding species and beam energies will be
discussed.
211.
Identical Meson Interferometry in STAR Experiment
Debasish Das (for the STAR Collaboration)
Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700064;
[email protected]; [email protected]
The influence of Bose-Einstein statistics on multi-particle production processes characterized
for various systems and energies by the STAR Collaboration provide interesting information about
the space-time dynamics of relativistic heavy-ion collisions at RHIC. We present the new
systematic analysis of the centrality and mT dependence of two-pion interferometry in Au+Au
collisions at √sNN = 62.4 GeV and Cu+Cu collisions at √sNN = 62.4 and 200 GeV. We compare the
new data with previous STAR measurements from p+p, d+Au and Au+Au[1] collisions at √sNN =
200 GeV. In all systems and centralities, HBT radii decrease with mT in a similar manner, which is
qualitatively consistent with collective flow[1]. The ratio, Rout/Rside, shows no sharp behavior with
collision energy, indicating a weak evolution of freeze-out timescales with energy density.
The scaling of the apparent freeze-out volume[2] with the number of participants and charged
particle multiplicity is studied. Measurements of Au+Au collisions at same centralities and different
energies yield different freeze-out volumes, which mean that Npart is not a suitable scaling variable.
The freeze-out volume estimates for all presented systems show a linear dependence as a function
of charge particle multiplicity. The multiplicity scaling of the measured HBT radii is found to be
independent of colliding system and collision energy.
References:
[1] J. Adams et al . (STAR Collaboration) Phys. Rev. C 71,044906 (2005).
[2] D.Adamova et al . (CERES Collaboration) Phys. Rev. Lett.90,022301 (2003).
212.
Scaling Properties of Fluctuation Measurements from PHENIX
Jeffery T. Mitchell, for the PHENIX Collaboration
Brookhaven National Laboratory
PHENIX has conducted a detailed survey of event-by-event charged hadron multiplicity
fluctuations as a function of centrality, transverse momentum range, and charge for the following
collision systems: 200 GeV Au+Au, 62 GeV Au+Au, 200 GeV Cu+Cu, 62 GeV Cu+Cu, 22.5
GeV Cu+Cu, 200 GeV p+p, and 200 GeV d+Au. After estimating and removing contributions due
to collision geometry fluctuations, large non-random fluctuations are observed for all species that
increase as centrality decreases. The fluctuations are extracted from fits to Negative Binomial
Distributions and plotted as the variance normalized by the square of the mean, which can be
directly related to the compressibility in the Grand Canonical Ensemble. The fluctuations exhibit
a power law behavior as a function of centrality that is identical for all collision species and
103
energies for the A+A systems, independent of the transverse momentum range of the
measurement. Possible interpretations of the observed scaling behavior and comparisons to SPS
results will be discussed. PHENIX has conducted a similar survey of event-by-event charged
hadron mean transverse momentum fluctuations. Non-random fluctuations are observed in all
systems that increase with transverse momentum. The datasets will be discussed in terms of scaling
properties as a function of centrality and collision energy, estimates of the heat capacity, and
contributions from hard scattering processes and elliptic flow.
VI.
QCD at High Temperature and Density
213.
Quark mass thresholds in QCD thermodynamics
Y. Schroder
Theoretical Physics, University of Bielefeld,
PO Box 100131, 33501 Bielefeld, Germany, [email protected]
We discuss radiative corrections to how quark mass thresholds are crossed, as a function of the
temperature, in basic thermodynamic observables such as the pressure, the energy and entropy
densities, and the heat capacity of high temperature QCD [1]. The indication from leading order that
the charm quark plays a visible role at surprisingly low temperatures, is confirmed. We also sketch
a way to obtain phenomenological estimates relevant for generic expansion rate computations at
temperatures between the QCD and electroweak scales, pointing out where improvements over the
current knowledge are particularly welcome.
References:
[1] M. Laine and Y. Schroder, Quark mass thresholds in QCD thermodynamics,''
Phys.\ Rev.\ D {\bf 73} (2006) 085009 [arXiv:hep-ph/0603048].
214.
Neutrino processes in normal and color superconducting quark matter
Qun Wang
Department of Modern Physics, University of Science and Technology of China
Anhui 230026, People's Republic of China, [email protected]
We study the phase space for neutrino emissions in direct Urca processes in normal and color
superconducting quark matter. We derive in QCD and the Nambu-Jona-Lasinio model the Fermi
momentum reduction resulting from Fermi liquid properties which opens up the phase space for
neutrino emissions. The relation between the Fermi momentum and chemical potential is found to
be
with
depending on coupling constants. We find in the weak coupling
regime that
is a monotonously increasing function of the chemical potential. It implies
quenched phase space for neutrino emissions at low baryon densities. Our findings can partly
narrow the huge gap between the cooling data of neutron stars and previous theoretical
predictions about direct Urca processes by slowing down the neutrino emission rate in both normal
and color superconducting quark matter due to the quenching of phase space.
Neutrino emissivities in direct Urca processes in several spin-one color-superconducting phases
of dense quark matter are calculated. In particular, the role of anisotropies and nodes of the gap
functions is analyzed. Results for the specific heat as well as for the cooling rates of the
color-spin-locked, planar, polar, and A phases are presented and consequences for the physics of
neutron stars are briefly discussed. Furthermore, it is shown that the A phase exhibits a helicity
order, giving rise to a reflection asymmetry in the neutrino emissivity.
References:
[1] Q. Wang, Z.g. Wang and J. Wu, arXiv:hep-ph/0605092, to appear in Phys. Rev. D.
[2] A. Schmitt, I. A. Shovkovy and Q. Wang, Phys. Rev. D73, 034012 (2006) [arXiv:hep-ph/0510347].
[3] A. Schmitt, I. A. Shovkovy and Q. Wang, Phys. Rev. Lett. 94, 211101 (2005) [arXiv:hep-ph/0502166].
104
215.
Pion-Pion-Sigma Mixing in Pion Superfluidity
Xuewen Hao
Department of Physics, Tsinghua University
Beijing, 100084, P. R. China, [email protected]
We investigate the static meson properties in pion superfluidity at finite isospin density. In the
frame of flavor SU(2) Nambu-Jona-Lasinio model, we discuss the meson mass splitting due to
explicit isospin symmetry breaking and the Goldstone mode corresponding to spontaneous isospin
symmetry breaking. Especially, we calculate the pion-pion-sigma mixing in the pion superfluid
phase, the mixing angles as functions of isospin chemical potential, and its effect on the sigma to
two pion process.
216.
Mesonic correlation functions at finite temperature and density
in the Nambu – Jona - Lasinio model with a Polyakov loop
H. Hansen(a) 1, W.M.Alberico(a), A.Beraudo(b), A.Molinari(a) , M.Nardi(a) , C.Ratti(c)
Sezione di Torino and Dipartimento di Fisica Teorica, University of Torino, via Giuria N.1,
10125 Torino - Italy
(b) Service de Physique Th´eorique, CEA Saclay, CEA/DSM/SPhT, F-91191, Gif-sur-Yvette - France
(c) ECT∗, 38050 Villazzano (Trento) - Italy
and INFN, Gruppo Collegato di Trento, via Sommarive, 38050 Povo (Trento) -Italy
(a) INFN,
We investigate the properties of scalar and pseudo-scalar mesons at finite temperature and
chemical potential in the framework of the Nambu–Jona-Lasinio (NJL) model complemented with a
Polyakov loop term (PNJL model, [1]). In an attempt of accounting both for the chiral symmetry
breaking and deconfinement (governed by the Polyakov loop in a pure gauge theory), quarks are
coupled to a background temporal gauge field.
We compute the mesonic correlators via the solution of the Schwinger–Dyson equation with
Hartree (mean field) quark propagator at finite temperature and density. It is shown that the
calculation of the PNJL loop integrals only required a modification of the Fermi–Dirac distribution
function that appeared in the NJL calculations.
From the spectral functions associated with the mesonic correlators, we deduce that the
mesonic widths obtained in PNJL are narrower than the ones of NJL at low temperatures and
densities whereas the opposite occurs for larger temperatures and densities. We finally discuss what
kind of confinement does the introduction of a Polyakov loop bring to the NJL model.
References:
[1] C. Ratti, M. A. Thaler, and W. Weise, Phys. Rev. D73, 014019 (2006).
217.
Gloun fluctuation-induced first order transition and
the complex energy gap in high density QCD
Defu Hou
Institute of particle physics,Central China Normal University
430079, Wuahn, China, [email protected]
We study the gauge field fluctuations and the complex energy gap in color-superconducting
phase of dense QCD. We find that gluonic fluctuations induce a strong first-order phase transition,
in contrast to a second order one without fluctuations and a weakly first order transtion in electronic
superconductors; Also we point out that the local approximation of the coupling between the gauge
potential and the order parameter,employed in the Ginzburg-Landau theory, has to be modified by
restoring the full momentum dependence of the polarization function of gluons in the
superconducting phase.
In weak coupling, we compute the critical temperature and
temperatures associated with the limits of metastability of the normal and superconducting phases,
as well as the latent heat associated with the first-order phase transition. We show that the critical
temperature for this transition is larger than the one corresponding to the diquark pairing instability
and find the London limit of magnetic interactions is absent in color superconductivity.
In
105
addition, we clarify general properties of the complex energy gap in dense QCD regarding its
functional dependence on the energy-momentum dictated by the invariance under a space inversion
or a time reversal. Then we derive perturbatively the equation of the imaginary part of the gap
function for dense QCD in weak coupling. We show that the imaginary part is down by $g$ relative
to the real part in weak coupling. The numerical results show that, up to the leading order,the
imaginary part is no larger than one MeV at extremely large densities and can be as large as several
MeV for the densities of compact stars.
References:
[1] Ioannis Giannakis, Defu Hou, Hai-cang Ren, Dirk H. Rischke,
Phys.Rev.Lett., V. 93, P. 232301 (4 pages), 2004
[2] Jorge L. Noronha, Hai-cang Ren, Ioannis Giannakis, Defu Hou, Dirk H. Rischke,
Phys.Rev. D\, v. 73, p. 0940009, 2006
[3] Defu Hou , Qun Wang , Dirk H. Rischke , Phys.Rev. D., V. 69, P. 071501, 2004
[4] Bo Feng, Defu Hou, Jia-rong Li, Hai-cang Ren, nucl-th/0606015
218.
Viscosity in the strongly interacting quark matter around the critical
temperature
LEVAI, Peter
MTA RMKI, Budapest, Hungary
I have investigated the viscosity coefficient in the deconfined matter around phase transition. At
first I have considered lattice-QCD results on the QGP EOS and introduced an appropriate
quasi-particle picture. Using the Arnold-Moore-Yaffe expressions, one can determine the viscosity
at finite temperature and can investigate it close to the phase transition. Because of the 1/log(1/alpha)
behaviour in the NLO expressions, divergencies may appear in the strongly interacting matter for
the viscosity, which indicates the limit of the validity of the pQCD calculations. On the basis of the
quasi-particle picture a molecular dynamical calculation can be performed in a quark-antiquark
dominated deconfined matter around the critical temperature. The pair-correlation function and
other microscopical quantities are determined, which are necessary to calculate viscosity in a
microscopical model. I compare the results of the above calculations and discuss the obtained
values for the viscosity of the strongly interacting quark matter.
219.
THE FREE ENERGY OF STATIC QUARKS IN FULL QCD
aThe
K. Petrov a and Bielefeld-RBC Collaboration
Niels Bohr Institute, Copenhagen, 2100, Denmark, [email protected]
I am going to present results from lattice calculations of the free energy of static quark
anti-quark ( QQ )and quark quark (QQ) pair at finite temperature. Calculation in full QCD with
almost realistic quark masses have been performed at the physical value of the strange quark mass
ms and several values of the u,d quark masses 0.05  mu ,d / ms  0.4 corresponding to pion mass
from 400 to 140 MeV. Monte-Carlo simulation have been done on Q This allows to control the
approach to the thermodynamic and continuum limits. The entropy contribution to the free energy is
separated and possible applications to the physics of heavy quarkonia at high temperature will be
discussed. The renormalized order parameter for the deconfinement transition is extracted and its
quark mass dependence will be discussed.
Please send all correspondence to K. Petrov, Niels Bohr Institute, Blegdamsvej 17, Copenhagen , 2100,
Denmark, [email protected]
220.
Static quark free energies at finite temperature in full QCD lattice simulations
Y. Maezawaa, S. Aokib S. Ejiria, T. Hatsudaa, N. Ishiia,
K. Kanayab, Y. Taniguchib and N. Ukitaa
aDepartment of Physics The University of Tokyo
106
Bunkyo-ku, Tokyo 113-0033, Japan, [email protected]
bInstitute of Physics, University of Tsukuba,Tsukuba, Ibaraki 305-8571, Japan
We study the free energies and potentials between static quarks at finite temperature by
performing numerical simulations of lattice QCD. The simulation is performed by using an
improved Wilson fermion action with two flavors.By using the projection operators into different
color channels of the heavy quarks (Q and¯Q), we extract the free energies in the color singlet Q¯Q
channel (1), octet Q¯Q channel(8), anti-triplet QQ channel (¯3), and sextet QQ channel (6). The
results are fitted by the screened Coulomb form above Tc:
where  (T) and mD(T) are the effective coupling constant and the Debye screening mass,
4
2
respectively. C(M) is the Casimir factor defined for each channel as C(1) =  , C( 3 ) =  , C(8)
3
3
1
1
= , C(6) =
: The results of  (T) and mD(T) are shown in fig. 1. We find that the channel
6
3
dependence of  (T) and mD(T) disappear if temperature is sufficiently high (T > 2.5Tc). This
implies that the perturbative form of the heavy quark free energy becomes valid at high
temperature.
Furthermore, we discussed the relation between lattice QCD and perturbative QCD, and the mD(T)
on a lattice is reproduced by the screening mass of next-to-leading order perturbation. These results
are also compared with previous results calculated by using the staggered fermion action, and we
find that the systematic error due to the difference of the action becomes smaller when temperature
increases, namely lattice spacing decreases.
Figure 1: The results of
channel.
 (T)(left) and mD(T)(right) as a function of temperature. Each color expresses each
221.
Further Analysis of Collective Excitations of Quarks at Finite Temperature
— mass effect and pole structure —
Kazuya Mitsutania, Masakiyo Kitazawab, Teiji Kunihiroa and Yukio Nemotoc
Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan
[email protected](K. Mitsutani), [email protected](T. Kunihiro)
bRIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973, USA,
[email protected]
cDepartment of Physics, Nagoya University, Nagoya 464-8602, Japan
[email protected]
aYukawa
The recent analyses of the RHIC experiment suggest that QGP near and above the critical
temperature Tc of QCD phase transition is a rather strongly coupled system. Such a picture is
consistent with the lattice calculations[1] and model calculations[2] which suggest the existence of
hadronic excitations even above Tc. In fact, the possible existence of hadronic excitation above Tc
107
itself had been suggested earlier by Hatsuda and Kunihiro[3]: They showed using an effective chiral
model that hadronic σ- and π-like excitations appear as the soft mode of the chiral transition near
but above Tc.
Recently Kitazawa et al[4] showed that the quarks may have a collective nature and show also
an anomalous behavior at T near but above Tc in the chiral limit: The quarks coupled to those soft
modes give rise to a three-peak structure in the spectral function. They also clarified with use of a
Yukawa model that the novel structure of the quark spectra is owing to a level mixing between
quark (anti-quark) states and anti-quark hole (quark hole) states in the thermally excited anti-quark
(quark) distribution via the “resonant scattering” of quarks with the soft modes.
In this report, we further examine their results on the anomalous behavior of the quarks focusing on
the pole structure of the collective quark excitations and the possible effects of the finite quark
mass. We find that the three-peak structure may or may not survive depending on the quark mass:
The finite quark mass largely affects the peak in the negative energy region of the three peaks in
the positive fermion number component of spectral functions. This result is found to be in
accordance with the interpretation by Kitazawa et al[4]; the finite quark mass works to shift the
quark energy to a higher energy, and hence the level mixing in the negative energy region is
suppressed. We have identified the poles of the collective quark excitations at various temperatures
for not only massless but also massive quarks. We show that the behavior of the quark spectra can
be nicely understood in terms of the pole behavior of the quarks. The relevance of our new findings
of the collective nature of the quarks to the RHIC experiments will be briefly discussed.
References:
[1] T. Umeda et al., Int. J. Mod. Phys., A 16, 2215, 2001; M. Asakawa and T. Hatsuda., Phys. Rev. Lett., 92,
012001, 2004; S. Datta et al., Phys. Rev., 094507, 2004
[2] E. Shuryak and I. Zahed., Phys. Rev., D 70, 054507, 2004; G. E. Brown et al., Nucl. Phys.,
A 740, 171, 2004; M. Mannarelli and R. Rapp, Phys. Rev., C 72, 064905, 2005
[3] T. Hatsuda and T. Kunihiro, Phys. Rev. Lett., 55, 158, 1985.
[4] M. Kitazawa et al., Phys. Lett., B 631, 157, 2005.
222.
POLYAKOV LOOP IN CHIRAL QUARK MODELS AT FINITE TEMPERATURE
E. Meg´ıasa, E. Ruiz Arriolab and L.L. Salcedoc
Granada, E-18071, Spain, Emails: [email protected], [email protected], [email protected]
We propose a model to couple the gluonic Polyakov loop in chiral quark models, and describe
how it drastically modifies finite temperature calculations after color neutral states are singled out.
This generates an effective theory of quarks and Polyakov loops as basic de- grees of freedom. We
find a suppression of finite temperature effects in hadronic observables triggered by approximate
triality conservation (Polyakov cooling), so that while the center symmetry breaking is
exponentially small with the constituent quark mass, chiral symmetry restoration is exponentially
small with the pion mass.
To illustrate the point we compute some low energy observables at finite temperature (vac- uum
expectation value of the Polyakov loop, chiral condensate, low energy structure of the chiral
effective Lagrangian up to
, and show that the thermal corrections are Nc sup- pressed
due to color average of the Polyakov loop. These corrections are provided by pion thermal loops,
with the standard power like e−mπ /T suppression at low temperatures. We extend the
computation to higher temperatures and study the implications for the simul- taneous center
symmetry breaking-chiral symmetry restoration phase transition. While the standard treatment of
chiral quark models at finite temperature systematically predicts a low temperature phase transition
as compared with lattice data, our model predict a higher value due to the Polyakov cooling
mechanism, with a more agreement with lattice studies. In particular, for a more accurate analysis
we start with a succesful fenomenological model to describe the lattice data for the Polyakov loop
above the deconfinement phase transition in quenched QCD [4], and study the effect of the quarks
on the phase transition according to the prediction of our Polyakov-Chiral Quark model.
108
This work is a continuation of a two works submitted for publication in Physical Review D
[5,6].
References:
[1] K. Fukushima, Phys. Lett. B591, 277 (2004). [arXiv: hep-ph/0310121].
[2] P.N. Meisinger, M.C. Ogilvie and T.R. Miller, Phys. Rev. D65, 034009 (2002).[arXiv: hep-ph/0108009].
[3] C. Ratti, M. A. Thaler and W. Weise, Phys. Rev. D73, 014019 (2006). [arXiv: hep-ph/0506234].
[4] E. Meg´ıas, E. Ruiz Arriola and L.L. Salcedo, JHEP 0601, 073, (2006). [arXiv: hep-ph/0505215].
[5] E. Meg´ıas, E. Ruiz Arriola and L.L. Salcedo, submitted to Physical Review D (2006). arXiv:
hep-ph/0412308.
[6] E. Meg´ıas, E. Ruiz Arriola and L.L. Salcedo, submitted to Physical review D (2006). arXiv:
hep-ph/0607338.
223.
DIMENSION TWO GLUON CONDENSATES AND THE HEAVY QUARK FREE ENERGY
E. Meg´ıasa, E. Ruiz Arriolab and L.L. Salcedoc
Granada, E-18071, Spain, Emails: [email protected], [email protected], [email protected]
We propose a phenomenological model to describe the available lattice data for the Heavy
Quark Free Energy in quenched (Nf=0) and unquenched (Nf=2) QCD in the deconfinement phase
[1,2]. These data exhibit unequivocal non perturbative contributions driven by a
dimension 2 gluon condensate. These contributions are characterized by power corrections of the
type 1/T 2, in contrast with the smooth behaviour of the perturbative contributions log(T ). A
matching of these lattice data allows us to obtain the r and T dependence of the running coupling
constant of QCD, which shows a smooth behaviour. This behaviour is in contrast with existing
analysis of this coupling constant at finite temperature [2].
We study the limit of large separation in the Heavy Quark Free Energy, to obtain the
renormalized Polyakov loop. Also, we study the limit of short separation to obtain the
Heavy Quark Potential at zero temperature. We observe a clear analogy (duality) between both
quantities, and obtain a relation between the dimension 2 gluon condensate and the string tension
which is numerically satisfied.
The corresponding (temperature dependent) potential thus obtained are then inserted into the
Schrdinger equation for the charmonium and bottonium. The solution of the equation provides an
estimate of the melting temperature and of the radii for the different cc and bb bound states.
This work is a continuation of the recently published [3]. See also [4,5].
References:
[1]O.Kaczmarek, F. Karsch, P. Petreczky and F. Zantow Phys.Lett.B543,41-47(2002).[arXiv: hep-lat/0207002 ].
[2] O.Kaczmarek, F. Zantow. Phys. Rev. D71 114510 (2005).[arXiv: hep-lat/0503017 ].
[3] E. Meg´ıas, E. Ruiz Arriola and L.L. Salcedo, JHEP 0601, 073, (2006).[arXiv: hep-ph/0505215].
[4] E.Meg´ıas, E. Ruiz Arriola and L.L. Salcedo, PoS(JHW2005)025, (2006).[arXiv: hep-ph/0511353].
[5] E.Meg´ıas, E. Ruiz Arriola and L.L. Salcedo, Romanian Reports in Physics, Vol.58, No.1,
81-85, (2006). [arXiv: hep-ph/0510114].
224.
The transition temperature in QCD with physical light and strange quark masses
Frithjof Karsch
for the RIKEN-BNL-Columbia-Bielefeld collaboration,Physics Department, Brookhaven National
Laboratory, Upton, NY 11973, USA , [email protected]
We present a detailed calculation of the transition temperature in QCD with two light and one
heavier (strange) quark mass on lattices with temporal extent Nτ = 4 and 6. Calculations with
improved staggered fermions have been performed for various light to strange quark mass ratios in
the range, 0.05 ≤ ml /ms ≤ 0.5, and with a strange quark mass fixed close to its physical value.
From a combined extrapolation to the chiral (ml → 0) and continuum (aT → 0) limits we obtain
the transition temperature at the physical point.
We also will report on the status of other calculations performed in this ongoing project of the
RBC-Bielefeld collaboration that aims at a controlled extrapolation of thermodynamic quantities to
109
the continuum limit by performing calulcations with improved staggered fermion discretization
schemes on lattices with different lattice cut-offs.
In particular, we will discuss
(i) new results on the equation of state for QCD with almost realistic light quark masses and a
physical value of the strange quark mass,
(ii) new results on hadronic fluctuations at vanishing quark chemical
potential and (iii) new results on the Taylor expansion of the QCD partition function at non-zero
baryon chemical potential.
References:
[1]N. H. Christ, M. Cheng, S. Datta, J. Van der Heide, C. Jung, F. Karsch, O. Kaczmarek, E. Laermann, R. D.
Mawhinney, C. Miao, K. Petrov, P. Petreczky, C. Schmidt and T. Umeda,
The transition temperature in QCD, BNL-preprint in preparation
225.
A field theoretical model for QCD thermodynamics
C. Rattia, S. Roßnerb and W. Weiseb
aECT*, Strada delle Tabarelle 286, Villazzano (Trento), I-38050, Italy, [email protected]
bPhysik-Department, Technische Universita¨t Mu¨nchen
Garching, D-85747, Germany, sroessn[email protected], Wolfram [email protected],
We study QCD thermodynamics at zero and finite quark chemical potential in the frame- work
of a Polyakov-loop-extended Nambu Jona-Lasinio model in which quarks couple simul- taneously
to the chiral condensate and to a background temporal gauge field representing Polyakov loop
dynamics [1, 2]. The parameters of the Polyakov loop effective potential are fixed in the pure
gauge sector. Chiral condensate and Polyakov loop as functions of temperature and quark chemical
potential are calculated by minimizing the thermodynamic potential of the system. The resulting
equation of state, (scaled) pressure difference and quark number density at finite quark chemical
potential µ are then obtained, both as Taylor expansions around µ = 0, and as full results at finite
µ. Remarkable agreement is found with the corresponding lattice QCD data. The validity of the
Taylor expansion is discussed within our model, through a comparison between the full results and
the truncated ones. We discuss the phase diagram as it emerges from this approach in close
comparison with results from lattice QCD thermodynamics. The critical point, separating crossover
from first order phase transition, is investigated with special focus on its quark mass dependence,
starting from the relatively large masses presently accessible by lattice simulations, down to the
chiral limit.
References:
[1] C. Ratti, M. A. Thaler and W. Weise, Phys. Rev. D 73, 014019 (2006).
[2] C. Ratti, M. A. Thaler and W. Weise, nucl-th/0604025.
226.
Simulation of the transition between meson-system
and QGP in a transport model
Tan Zhiguang a and A.Bonasera b
Institute of Particle Physics, Hua-zhong normal university,
Wuhan, 430079, China, [email protected]
b) Laboratorio Nazionale del Sud, Istituo Nazionale Di Fisica Nucleare,
Via S.Sofia 44,I-95123 Catania, Italy, [email protected]
a)
We use a transport model based on the mean free path approach to simulate an interacting
meson system at finite temperature, and discuss some equilibrium features of the system. For a pure
meson gas where the Hagedorn limiting temperature is reproduced when including the
experimentally observed resonances. We can easily include the possibility of a QGP using the bag
model. After a lifetime the quarks can recombine to resonances or string which will decay or break
into various mesons. Our results for different numbers of flavors Nf compare very well to LQCD
results. In particular the crossover to the QGP at temperature about 175 Mev is nicely reproduced.
Quantum statistics (i.e. Fermi and Bose statistics) are included also.
110
References:
[1] F.Kartsch, Nucl.Phys. A698,199c(2002).
[2] Bin Zhang, Comput.Phys. Commun. 109,193(1998).
[3] Ben-Hao Sa and An Tai, Phys.Rev. C 62, 044905(2000).
[4] Ben-Hao Sa and A. Bonasera, Phys. Rev. C 70, 034904 (2004)
227.
Thermodynamics of two-flavor lattice QCD with an improved
Wilson quark action at non-zero temperature and density
S. Ejiria, S. Aokib, T. Hatsudaa, N. Ishiia, K. Kanayab, Y. Maezawaa, Y. Taniguchib, N. Ukitaa
of Physics, The University of Tokyo, Tokyo 113-0033, Japan, [email protected]
b
Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
We discuss the equation of state for QCD in the low density regime by performing numerical
simulations of lattice QCD. The studies of the equation of state can provide basic input for the
analysis of the experimental signatures for QGP formation and are very important. However, most
of numerical simulations have been done by using staggered type quark actions, therefore studies
by a different formulation of quarks on a lattice is necessary to confirm the reliability of the results
from lattice QCD simulations.
We perform simulations of two-flavor QCD with an improved Wilson quark action and
calculate the Taylor expansion coefficients of the thermodynamic grand partition function in terms
of chemical potential up to fourth order. These enable us to estimate the pressure,the quark number
density and its susceptibility as a function of the chemical potential in
the low density regime. Moreover these results are compared to previous results obtained by
simulations with staggered type quarks.
228.
LANDAU POTENTIAL STUDY OF THE CHIRAL PHASE TRANSITION IN A QCD-LIKE
THEORY
Y. Tsuea, H. Fujiib and Y. Hashimotoc
Division, Faculty of Science, Kochi University
Kochi 780-8520, Japan, [email protected]
bInstitute of Physics, The University of Tokyo,Tokyo 153-8902, Japan, [email protected]
cPhysics Division, Faculty of Science, Kochi University, Kochi 780-8520, Japan
aPhysics
The phase structure of quantum chromodynamics (QCD) at finite temperature T and quark
chemical potential µ is actively investigated in the context of the collider experiments using
ultra-relativistic heavy ion beams which would lead to the highly-excited QCD matter. Also,
extremely dense hadronic matter is relevant to the physics of the inner structure of neutron stars.
The chiral symmetry of QCD, which is spontaneously broken in the vacuum, will be restored at
sufficiently high temperature and/or quark chemical potential. Thus, many model studies have been
carried out and have provided information concerning the in-medium properties of QCD.
Here, we investigate the chiral phase transition based on a QCD-like theory, focusing on the
shape change of the effective potential. The QCD-like theory is the renormalization-group improved
ladder approximation for the Schwinger-Dyson equation of QCD. This theory describes the
dynamical chiral symmetry breaking while retaining the correct high energy behavior of the quark
mass function. Using this theory and the low-density expansion, the pion-nucleon sigma term and
the quark condensate at finite density have been calculated[1]. The Cornwall-Jackiw-Tomboulis
(CJT) potential functional has been used in several works for the study of dynamical chiral
symmetry breaking. However, the interpretation of the CJT potential away from the extremum is
not obvious.
Thus, in order to investigate the global behavior of the chiral phase transition through the shape
change of the effective potential, we construct the Landau potential of the QCD-like theory by using
the auxiliary field method, in which the bilocal external field is introduced[2]. This Landau
potential depends on the quark condensate and the quark number density with fixed temperature and
quark chemical potential. Plotting the contour map with respect to the quark condensate and the
111
quark number density, the global behavior of the chiral phase transition can be elucidated. As one of
the obtained results, for example, it is shown that the tri-critical point is located at (T , µ) = (97, 203)
MeV.
References:
[1] H. Fujii, and Y. Tsue, Physics Letters B , v. 357, p. 199-203, 1995.
[2] Y. Hashimoto, Y. Tsue, and H. Fujii, Progress of Theoretical Physics , v. 114, p. 595-608, 2005.
229.
DYNAMICS IN EVOLUTION OF BULK QCD MATTER AT RHIC
Chiho Nonakaa and Steffen A. Bassb
Department of Physics, Nagoya University,Nagoya 464-8602, Japan
[email protected]
bDepartment of Physics, Duke University, Durham, NC 27708, USA, [email protected]
a
We introduce a combined fully three-dimensional macroscopic/microscopic transport approach
employing relativistic 3D-hydrodynamics for the early, dense, deconfined stage of the reaction and
a microscopic non-equilibrium model for the later hadronic stage where the equilibrium
assumptions are not valid anymore. Within this approach we study the dynamics of hot, bulk QCD
matter, which is being created in ultra-relativistic heavy ion collisions at RHIC. Our approach is
capable of self-consistently calculating the freezeout of the hadronic system, while accounting for
the collective flow on the hadronization hypersurface generated by the QGP expansion. In particular,
we perform a detailed analysis of the reaction dynamics, hadronic freezeout, transverse flow and
elliptic flow. Furthermore we study the sensitivity of observables regarding the QCD critical point
using a more realistic equation of state which is suggested by the lattice QCD. We will also
investigate the sensitivity of two particle correlations (HBT) on the initial conditions of the 3D
hydro + UrQMD model.
References:
[1] Chiho Nonaka and Steffen A. Bass, nucl-th/0607018.
[2] Chiho Nonaka and Masayuki Asakawa, Phys. Rev. C71, 044904 (2005).
230.
Unified description of deconfined QCD equation of state
A. Ippa, K. Kajantieb, A. Rebhanc, and A. Vuorinend
ECT*, Villa Tambosi, Strada delle Tabarelle 286,I-38050 Villazzano Trento, Italy, [email protected]
bDepartment of Physics, P.O. Box 64, FI-00014 University of Helsinki, Finland, [email protected]
cInstitut fu¨r Theoretische Physik, Technische Universit¨at Wien,
Wiedner Hauptstr. 8-10, A-1040 Vienna, Austria, [email protected]
dDepartment of Physics, University of Washington,
Seattle, WA 98195, U.S.A., [email protected]
a
We present a new method for the evaluation of the perturbative expansion of the QCD pressure
which is valid at all values of the temperature and quark chemical potentials in the deconfined
phase and which we work out up to and including order g4 accuracy. In various limits, we recover
the known results of dimensional reduction and the HDL and HTL resummation schemes, as well as
the equation of state of zero-temperature quark matter, thereby verifying their respective validity. To
demonstrate the overlap of the various regimes, we furthermore show how the predictions of
dimensional reduction and HDL resummed perturbation theory agree in the regime T∼√gµ. At
parametrically smaller temperatures T
gµ, we find that the dimensional reduction result agrees
well with those of the nonstatic resummations down to the remarkably low value T ≈ 0.2mD , where
mD is the Debye mass at T = 0. Beyond this, we see that only the latter methods connect smoothly
to the T = 0 result of Freedman and McLerran, to which the leading small-T corrections are given
by the so-called non-Fermi-liquid terms, first obtained through HDL resummations. Our work
unifies previous perturbative approaches and provides a systematic and complete perturbative
description of the equation of state of the quark gluon plasma in the deconfined phase.
References:
[1] A. Ipp, K. Kajantie, A. Rebhan and A. Vuorinen, The pressure of deconfined QCD for all temperatures and
112
quark chemical potentials, arXiv:hep-ph/0604060, (accepted for publication in PRD).
231.
Qurak Spectrum above the critical Temperature from the Schwinger-Dyson Equation
Masayasu Harada, Yukio Nemoto and Shunji Yoshimoto
Department of Physics, Nagoya University,Nagoya, 464-8602, Japan,
[email protected]
In gauge-fermion system such as QCD or QED, it is well known[1] that the massless fermion
obtains an effective mass through the interaction with heat bath, and that a collective mode called
plasmino emerges in addition to the ordinary particle. The effective masses of such modes are
proportional to the temperature and the coupling constant in the weak coupling region. On the
other hand, the state observed at RHIC strongly suggests[2] that the cou- pling is very strong near
the critical temperature, which indicates that it is important to take account of non-preturbative
effects.
We study the fermionic spectral function above the critical temperature for the chiral phase
transition using the Schwinger-Dyson equation to include a non-perturbative effect. In this analysis,
we first solve the Schwinger-Dyson equation for the fermion propagator in the ladder
approximation within the imaginary time formalism. Then we obtain a fermionic spectral function
by performing the analytic continuation to Minkowski space using an integral equa- tion, the
Schwinger-Dyson equation itself. When the coupling is very weak, the spectral function has two
sharp peaks and the peak positions of the spectral function almost coincide with the pole position
obtained at one-loop. We find that, even in the strong coupling region, there exists a peak
corresponding to the plasmino in addition to the peak corrresponding to the particle. Furthermore,
both of the peaks are very broad, and the energies at these peaks are lower than those at one-loop.
References:
[1] H. A. Weldon, Phys. Rev. D 26, 2789 (1982); H. A. Weldon, Phys. Rev. D 40, 2410 (1989); H. A. Weldon,
Phys. Rev. D 61, 036003 (2000).
[2] M. Gyulassy and L. McLerran, Nucl. Phys. A 750, 30 (2005).
232.
Phase diagram at finite temperature and quark density
in the strong coupling limit of lattice QCD for color SU(3)
A. Ohnishi, N. Kawamoto, K. Miura, T. Ohnuma
Department of Physics, Faculty of Science, Hokkaido University
Sapporo 060-0810, Japan, [email protected]
Exploring various phases of quark and nuclear matter has attracted much attention in recent years.
QCD phase transition at high temperature and zero baryon density is predicted from lattice QCD,
which is supported by recent experiments at RHIC suggesting the forma- tion of sQGP. On the other
hand, various interesting forms of matter have been proposed so far including the color
superconductor in cold and dense baryonic matter. Since it is not easy at present to give reliable
predictions in Monte-Carlo simulations of the lattice QCD for the properties of highly compressed
and cold matter µ/T ≥ 1, it is highly desired to discuss the whole phase diagram of quark matter in
well-defined frameworks/approximations based on QCD.
One of the promissing approximations would be to consider the strong coupling limit of lattice
QCD. In fact effective free energy at finite T has been derived analytically, and it predicts the
second order chiral phase transition at finite T. In many of these works, while the mesonic
composite M= qq is taken into account, the effect of baryonic compoisites B =  q a qb q c is
abc
ignored. The latter would be important in cold dense matter and then for the discussion of the whole
phase diagram.
In this work, we study the phase diagram of quark matter at finite temperature (T ) and finite
chemical potential (µ) in the strong coupling limit of lattice QCD for color SU(3) with one species
of staggered ferimon [1]. We derive an analytical expression of the effective free energy as a
function of T and µ, including baryon composite effects. The finite temperature effects are
113
evaluated by integrating over the temporal link variable exactly in the Polyakov gauge with
anti-periodic boundary condition for fermions. The obtained phase diagram shows the first order
phase transition at low temperatures and the second order phase transition at high temperatures
separated by the tri-critical point in the chiral limit. Baryon has effects to reduce the effective free
energy and to extend the hadron phase to a larger µ direction at low temperatures.
In the presentation, we also mention the application of the strong coupling limit lattice QCD
results to nuclear physics [2], and recent results with two species of staggered fermions.
References:
[1] N. Kawamoto, K. Miura, A. Ohnishi, T. Ohnuma, hep-lat/0512023.
[2] K. Tsubakihara and A. Ohnishi, nucl-th/0607046.
233.
Nucleon-Nucleon
Potential from Lattice QCD
N. Ishiia , S. Aokib, and T. Hatsudaa
a
Department of Physics, University of Tokyo
7–3–1 Hongo, Tokyo 113–0033, JAPAN, [email protected] and [email protected]
bGraduate School of Pure and Applied Science, University of Tsukuba
Tsukuba 3005–8571, Ibaraki, JAPAN, [email protected]
The nuclear force serves as one of the most important building blocks in the nuclear physics. Its
attractive part appearing at the intermediate to long distance is indispensable in forming nuclei,
whereas its repulsive core existing at short distance plays the essential role for the saturation of the
nuclear matter density. In spite of its importance, the theoretical under- standing of nuclear force
involves number of uncertainties especially at short distance( r < 1 fm), where only the
phenomenological approaches are available. Since this region should reflect the quark-gluon
degrees of freedom as well as the internal structure of nucleon, it has been desired for a long time to
be understood in terms of QCD itself. However, the lattice QCD calculation requires a tough
numerical calculation. In this talk, we present the 1st lattice QCD result for the nuclear force[1] by
using a method, which was recently proposed by CP-PACS collab. and was applied to the ππ system
for the scattering length[2]. With this method, we identify the Bethe-Salpeter(BS) wave function for
NN system as the Schr¨odinger wave function. Then, the NN potential is reconstructed so that the
NN Sch¨odinger equation is satisfied. Below, we present a quenched lattice QCD result for the NN
potential Vcentral (r) in (J P ,T ) = (0+, 1), where a simplification is allowed, since the contributions
from the tensor and the LS terms vanish in this channel.
For this calculation, we employ the standard Wil- son gauge action on 163 × 24 lattice at β =
5.7 and the Wilson quark action with κ = 0.1665(strange quark mass region), which leads to the
lattice spacing a−1 = 1.44 GeV and mπ  0.52 GeV. In this figure, we observe a repulsive core at
short distance. However, the attraction in the interme- diate to long distance is missing. This may be
attributed to the still heavy quark mass and to the small lattice size L  2.25 fm. For improvement,
we are currently performing a lattice QCD calculation with a smaller quark mass on a larger lattice,
114
which we are going to present at the QM2006.
References:
[1] N. Ishii, S. Aoki, T. Hatsuda, “Nuclear Force from Lattice QCD”, a talk given at The XXIV International
Symposium on Lattice Field Theory, Tucson, Arizona, July 23–28, 2006.
[2] CP-PACS Collab., S. Aoki et al., Phys. Rev.D71,094504(2005).
234.
Hadron-quark continuity induced by the axial anomaly in dense QCD
Naoki Yamamoto,a Tetsuo Hatsuda,a Motoi Tachibana,b and Gordon Baymc
Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
[email protected] and [email protected]
bDepartment of Physics, Saga University, Saga 840-8502, Japan, [email protected]
c
Department of Physics, University of Illinois, Illinois 61801, [email protected]
a
The transition from the hadronic Nambu-Goldstone (NG) phase of dense matter to the
deconfined color-superconducting (CSC) phase is relevant to heavy ion collisions to be explored in
the future at moderate energies at GSI, and of interest in the interiors of neutron and quark stars.
The NG-to-CSC transition depends critically on the interplay between two competing phenomena:
quark–anti-quark pairing, characterized by a chiral condensate  qq  hq¯qi, and quark-quark
pairing, characterized by a diquark condensate  qq  . This competition is interesting not only in
QCD, but also in relation to similar phenomena in other systems, e.g., the transition between
magnetically ordered phases and metallic superconductivity.
We have investigated the interplay between the two condensates within the framework of the
Ginzburg-Landau (GL) free energy for QCD with two and three massless flavors. Our
model-independent analysis is based only on the QCD symmetries G ≡ SU (Nf )L × SU (Nf )R × U
(1)B × U (1)A × SU (3)C , where U (1)A is explicitly broken by the axial anomaly. As we show, the
QCD axial anomaly under the influence of the diquark condensate acts as an external field applied
to the chiral condensate. Then, the first order chiral transition at finite density is changed to a
crossover for large diquark condensate, and a new critical point driven by the axial anomaly
emerges in the QCD phase diagram [1].
FIG. 1: Schematic phase structure with two light
quarks (up and down) and a medium heavy quark
(strange). The phase boundaries with a first (second)
order transition is de- noted by a double (single) line.
The arrows show how the critical point and the
phase boundaries move as the strange-quark mass
in- creases toward the two-flavor limit.
We discuss the implications of this new critical
point at high baryon density. Also, we report our recent study of the elementary excitations in our
GL approach and the relationto the hadron-quark continuity proposed in [2].
Reference:
[1] T. Hatsuda, M. Tachibana, N. Yamamoto, and G. Baym, hep-ph/0605018.
[2] T. Scha¨fer and F. Wilczek, Phys. Rev. Lett. 82, 3956 (1999).
VII. Low-x Parton Dynamics and Parton Saturation
235.
ARE THERE MONOJETS
IN HIGH-ENERGY PROTON--NUCLEUS COLLISIONS?
115
N.Borghini a and F.Gelis b
a
CERN , Physics Department, Theory Division
CH-1211 Geneva 23, Switzerland, [email protected]
b
Service de Physique Theorique, bat. 774, CEA/DSM/Saclay, F-91191 Saclay cedex, France
We study proton--nucleus collisions at high energy in the Color Glass Condensate framework,
and extract from the gluon production cross-section the probabilities of having a definite number of
multiple scatterings in the nucleus with amomentum transfer larger than a given cut. Various
properties of the distribution in the number of multiple scatterings are considered, and we conclude
that events with monojets, i.e., where the momentum of a hard jet is compensated by many soft
particles on the opposite side, are very unlikely, except for extreme values of the saturation scale
Qs .
236.
ENERGY DEPENDENCE OF NUCLEAR SUPPRESSION IN
THE FRAGMENTATION REGION
K .Tywoniuk a ,  , I .C. Arsene a , L.Bravina a ,b , A.B.Kaidalov c and E.Zabrodin a ,b
a
Department of Physics, Universit y of Oslo
P.O. Box 1048 Blindern, 0316 Oslo, Norway,
b

Institute of Nuclear Physics, Moscow State , RU-119899 Moscow, Russia
c
Institute of Theoretica l and Experiment al Physics , RU-117259 Moscow, Russia
Recent measurements of the nuclear modification factor for hadron-nucleus collisions at SPS,
Fermilab and RHIC for xF  0 have been analyzed for a wide range of energies,
s  17.3  200GeV , and a model including energy-conservation effect, Cronin effect and gluon
shadowing is presented. The suppression of the nuclear modification factor is not increasing
substantially with growing s , leaving therefore little room for shadowing or saturation effects at
RHIC, assuming that energy-conservation effect is constant in energy. We show that gluon
shadowing becomes significant only in the most forward region of d+Au collisions at s GeV. This
is also supported by the fact, that the dependence of soft particle production in d+Au collisions at
RHIC as a function of xF on the nuclear number, parameterized by A ( xF ) , follows the trend of
low-energydata. Energy-momentum conservation and Cronin effects areparameterized within a
Glauber inspired model, while gluon shadowing is calculated within the Glauber-Gribov model. We
also make predictions for the expected suppression at LHC energy, s =5.5 TeV.
[1] K .Tywoniuk , I .C. Arsene, L.Bravina , A.B.Kaidalov and E.Zabrodin , hep-ph/0510371
237.
QQ  production in pA collisions at RHIC and the LHC
Javier L. Albacete a , Yuri V. Kovchegov a and Kirill Tuchin
a
b,c
Department of Physics, The Ohio State Universit y
Columbus, Ohio, 43201, USA, [email protected], [email protected]
b
Department of Physics and Astronomy, Iowa State
University, Ames, IA 50011, USA, [email protected]
c
RIKEN BNL Research Center, Upton, NY 11973 - 5000
Heavy flavor production is considered to be a valuable probe for studying QCD properties of
the dense medium formed in heavy ion collisions. However, the heavy quark production mechanism
in a nuclear enviroment is still poorly understood, since it is characterized by two hard scales (the
saturation scale and the quark mass) with a non-trivial interplay. In this talk I will present a
116
calculation for quark-antiquark production cross-section in proton-nucleus collisions at high
energies, valid for both light and heavy quark production. The calculation is performed in the
framework of the Color Glass Condensate, resumming multiple scatterings at a quasi-classical level
first and implementing quantum effects via non-linear evolution in the limit of large number of
colors (BK) afterwards. Comparison with currently available RHIC experimental data will be
presented as well as predictions for the LHC, discussing in detail the collision energy, centrality,
rapidity and transverse momenta dependence of the produced pair. Deviations of heavy-quark
production from the pQCD collinear factorization scheme will be also discussed.
238.
Identified hadron production in d+Au and p+p collisions at RHIC
H.Yang a for the BRAHMS Collaboration
a
Department of Physics and Technology , Universit y of Bergen
Bergen, 5007, Norway,
[email protected]
The rapidity dependence of the inclusive transverse momentum ($p_T$) spectra of identified
hadrons from d+Au collisions with respect to p+p interactions at RHIC energy provides a clean
probe to disentangle different aspects of the collision dynamics, such as the soft/hard parton
scattering at the initial stage of collision and the final-state hadronization. One can study nuclear
effects via the nuclear modification factor
d 2 N d  Au / dpT dy
,
RdAu 
p p
 N bin  d 2 N inel
/ dpT dy
and its dependence on rapidity which may shed light on two different effects at the initial stage of
the collision, namely multiple scattering and parton saturation. Particle ratios, like K /  , p /  , as
well as the like-particle ratios at different rapidities provide insight into the hadro-chemistry of the
system. The net-proton distributions are instructive for understanding the collision cenario, e.g. the
baryon transport mechanism.
The BRAHMS experiment has measured the pT pectra of charged pions, kaons and
protons/anti-protons overa large rapidity range (-0.2<y<3.5) in d+Au (min-bias and 3 different
centralities from run03 data) and p+p collisions (from run05 data) at s NN =200GeV. RdAu has
been constructed and shows a mass and rapidity dependence as compared to RCP , and also RdAu is
to be compared with various models, especially atforward rapidity (small x region). The pT
spectra have been fitted to power-law, exponential in mT and Boltzmann functions for pions,
kaons and protons respectively. The rapidity dependence of the integrated yields and the ratios
( K /  , p /  ) will also be shown. The net-proton rapidity distribution ("stopping") in p+p and d+Au
will be compared to model expectations.
239.
Probing small-x gluons and large-x quarks: jet-like correlations between
forward- and mid-rapidity in pp, d+Au, and Au+Au collisions from STAR
Levente Molnara for the STAR Collaboration
aDepartment of Physics, Purdue University,West Lafayette, IN, 47906, USA,
[email protected]
Mid-rapidity back-to-back azimuthal correlations probe di-jets originating mainly from small-x
gluon-gluon hard-scatterings. Measurements of such correlations have revealed significant
(gluon-)jet modification in central Au+Au collisions. Azimuthal correlations at forward-rapidity
with a mid-rapidity high-pT particle, on the other hand, are sensitive primarily to hard-scatterings
between large-x quarks and small-x gluons, and thereby may probe quark-jet modification in
nuclear medium as well as the onset of gluon saturation in the forward rapidity region. In this talk,
117
we will present results from STAR on correlations of charged hadrons at forward rapidity in the
Forward Time Projection Chambers (2.7 <||< 3.9, pT < 2 GeV/c) with high-pT charged hadrons at
mid-rapidity from the main TPC (|| < 1, pT > 3 GeV/c). Preliminary results from 200 GeV pp,
d+Au, and Au+Au collisions of varying centralities will be presented. Implications of the results in
terms of jet-medium interaction at forward rapidity and the Color Glass Condensate will be
discussed.
240.
Nuclear modification to parton evolution and onset of parton saturation
Zhongbo Kang a and Jian-Wei Qiu b
Department of Physics and Astronomy,Iowa State University, Ames, Iowa 50011, USA}
a
[email protected] b [email protected]
Nuclear dependence is an excellent probe of nuclear structure and dynamical properties of
strong interacting medium produced in high energy nuclear collisions. Understanding the features
of different sources of nuclear dependence is extremely important for discovering new properties of
QCD and strong interaction physics.
In this talk, we will present a new systematic calculation of the universal (or process
independent) nuclear dependence to nuclear parton distribution functions (nPDFs) [1]. To be
consistent with QCD factorization of hard probes, we followed the collinear QCD factorization
approach. We derived a new set of modified DGLAP parton evolution equations for nPDFs by
calculating both real and virtual Feynman diagrams without using the AGK cutting rule. Therefore,
our result is not limited to a region of very small x, and has an advantage for studying the transition
region between the regimes of dilute and saturated partons.
This new set of evolution equations includes all powers of the  s A1 / 3 / Q 2 -type of leading
nuclear size enhanced contributions, expressed in terms of multiparton correlation functions well-defined multiple parton matrix elements. With one simple assumption for nuclear wave
function, this set of parton evolution equations can be reduced to a compact and closed set of
evolution equations for nPDFs with only one unknown but universal matrix element. Using the
matrix element whose value is consistent with nuclear dependence observed in Drell-Yan and
inclusive Deep Inelastic Scattering (DIS), we found that gluon evolution at small parton momentum
x and low Q 2 is significantly modified. The modification significantly slows down the growth of
gluon density as x decreases. This new set of parton evolution equations is consistent to the
existence of parton saturation phenomena and offers a prescription to approach to and identify the
saturation regime.
References
[1] A part of preliminary results was first presented by J. Qiu at the 5th International Conference on Perspectives
in Hadronic Physics'' held at the Abdus Salam International Centre for Theoretical Physics (ICTP) in Trieste from
22 to 26 May, 2006. Several new results have been obtained since then and a manuscript is being prepared for
publication.
Corresponding Author:
Jianwei Qiu
Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA [email protected]
VIII. Quark Matter in Astro-particle Physics
241.
Phase Diagram of Color Superconductivity with Spin-0 and Spin-1 Pairings
Xuguang Huang
Physics Department, Tsinghua University, Beijing, 100084, P. R. China
[email protected]
The Cooper pairs in color superconductivity can have two possible spin-flavor correlations, one
is the total spin-0 channel with antisymmetric flavor structure and the other is the total spin-1
118
channel with symmetric flavor structure. For the two flavor color superconductivity with chemical
potential mismatch between u and d quarks, the spin-0 superconductivity is in BCS state at low
mismatch and in LOFF state at high mismatch. However, when the spin-1 channel is taken into
account, there is a phase transition from the spin-0 to spin-1 superconductivities, and the LOFF
state at low temperature is eaten up by the spin-1 superconductivity. There is no phase permiting the
mixture of these two types of pairing. The phase diagram is presented on the temperature and
chemical potential mismatch plane.
242.
Neutral Dense Quark Matter at Intermediate Temperatures
Lianyi He
Physics Department, Tsinghua University, Beijing, 100084, P. R. China,
[email protected]
The temperature effect and density effect on the phase structure of neutral color
superconducting quark matter are quite different. While the Meissner masses squared for some
gluons behave unconventionally at zero temperature which indicates chromomagnetic instability,
they return to the classical case near the critical temperature. Therefore, the uniform 2SC/g2SC
phase is stable in a temperature region below but close to the critical temperature. We further show
that, this stable 2SC/g2SC phase is also stable against phase separation or mixed phase. We
analytically prove that the turning temperatures for the Meissner masses squared to change from
positive to negative are just the limiting temperatures of the LOFF and gluonic phases. When the
LOFF phase is taken into account at low temperatures, the strange intermediate temperature
2SC/g2SC becomes unrealistic, which will significantly change the phase diagram of neutral dense
quark matter.
243.
Hyperon-Quark Mixed Phase in Compact Stars
Toshiki Maruyama a,(*) , Toshitaka Tatsumi b ， Hans - Josef Schulze c ， Satoshi Chiba a
a
Advanced Science Research Center, Japan Atomic Energy Agency,
Tokai, Ibaraki, 319-1195, Japan, [email protected]
b
Department of Physics, Kyoto Universit y, Kyoto, 606-8502, Japan
c
INFN Sezione di Catania,Via Santa Sofia 64, Catania, I-95123, Italy
Quark matter has been expected to exist inside compact stars. The deconfinement transition
from hadron to quark phase may occur at high density as a first-order phase transition (FOPT).
Then the quark-hadron mixed phase should appear during such FOPT, where charge density as well
as particle density becomes nonuniform [1]. Owing to the Coulomb interaction and the surface
tension between two phases, the mixed phase can have an exotic shape called pasta structure [2-5],
which affects the mechanical and thermodynamical properties of matter. Recently there are many
studies about the mixed phase, but a simple treatment (sometimes called a bulk Gibbs calculation)
has been often done without taking into account the non-uniform structure. In a series of papers we
have carefully treated such nonuniform structure, based on the Gibbs criteria [4,5]. Particularly, we
have emphasized an important role of the charge screening effect for the Coulomb interaction; it
sometimes causes a mechanical instability of geometrical structures in the mixed phase. By a bulk
Gibbs calculation the quark-hadron mixed phase has been shown to be in a wide density region [1].
However, we have numerically shown that the charge screening largely affects the structure and
limits the region of the mixed phase (see Fig.~1) [4,5]. There, we have not taken into account
hyperon degrees of freedom in hadron phase, while they should be important at high density. In this
presentation, we incorporate a realistic equation of state of hadronic matter with hyperon degrees of
freedom [6] and discuss the property of hyperon-quark mixed phase in compact stars.
119
References
[1] N.K.Glendenning, Phys.Rev.D, v.46, p.1274, 1992; Phys.Rep., v.342, p.393, 2001.
[2] D.G.Ravenhall, C.J.Pethick and J.R.Wilson, Phys.Rev.Lett., v.50, p.2066, 1983.
[3] M.Hashimoto, H.Seki and M.Yamada, Prog.Theor.Phys., v.71, p.320, 1984.
[4] T.Maruyama et al., Phys.Rev.C, v.72, 015802, 2005; Phys.Rev.C, v.73, 035802, 2006; nucl-th/0605075, to
appear Recent Research Developments in Physics.
[5] T.~Endo et al., Prog.Theor.Phys., v.115, p.337, 2006.
[6] M.Baldo, G.F.Burgio and H.J.Schulze, Phys.Rev.C, v.61, 055888801, 2000.
244.
BLACK HOLE FORMATION DURING THE QCD PHASE
TRANSITION IN THE EARLY UNIVERSE
a
J. I. Kapusta and T. Springer
a
School of Physics and Astronomy, University of Minnesota
Minneapolis, MN 55455, USA, it [email protected]
b
School of Physics and Astronomy, University of Minnesota
Minneapolis, MN 55455, USA, [email protected]
b
It was first suggested by Jedamzik a decade ago that solar mass black holes could have been
formed during a first order QCD phase transition in the early universe. The reason is that during a
first order phase transition the speed of long wavelength sound waves is zero, implying a softened
equation of state that would allow overdense regions of space to more easily collapse to a black
hole. We have studied the critical overdensity necessary to achieve collapse for a variety of QCD
equations of state, including various parametrizations of a first order phase transition, a second
order phase transition, and a rapid crossover. Limits on the abundance of primordial black holes
from Jupiter mass to solar mass can provide information on the QCD equation of state.
245.
Two step conversion of Neutron star to Strange star
a
Ritam Mallick, Abhijit Bhattacharyya, Sanjay K. Ghosh，Partha S. Joarder, Sibaji Raha
a
Department of Physics; Bose Institute; 93/1, A.P.C Road; Kolkata - 700009; INDIA
b
Department of Physics; University of Calcutta; 92, A.P.C Road; Kolkata - 700009; INDIA
Neutron star is envisaged to be a laboratory for studying the phase transition process in strongly
interacting matter. Such transition may be viewed as a two step process in which the hadronic
matter first gets converted to a two-flavour quark matter that, in turn, converts to a strange quark
matter in the second step of the process. In this paper, we present a preliminary study of such phase
conversion process in neutron stars. We consider a relativistic mean field EOS for the hadronic
matter in a neutron star. Density profile of the hadronic matter is then obtained from the solution of
the TOV equations. We further consider a Bag model EOS for the quark matter in the star.
Relativistic hydrodynamical equations are employed to obtain the velocity of propagation of the
first conversion front. The second transition front, arising due to the conversion of two-flavour to
three-flavour quark matter, is here studied by using an approppriate weak interaction rate. Our
results show that the propagation velocity of the first conversion front initially shoots up near the
core of the star to eventually saturate to some ultrarelativistic value. It might take about a
millisecond to convert the entire hadronic matter to a two-flavour quark matter in the first step,
during which the second conversion front is likely to be generated. The second process should take
120
about a hundred second to convert the whole quark star into a strange star.
246.
Modern quark matter equations of state vs. compact star observations
David Blaschke
Institute of Physics, Rostock University, Germany, Bogoliubov Laboratory for Theoretical Physics,
JINR Dubna, Russia, [email protected]
Recently, observations of compact stars have provided new data of high accuracy which put
strong constraints on the high-density behaviour of the equation of state of strongly interacting
matter otherwise not accessible in terrestrial laboratories [1]. The simultaneous measurement of
high mass (M > 2 M¯), radius (R > 12 km) and surface redshift (z = 0.35) for EXO 0748-676 [2]
rules out soft equations of state and has provoked a debate whether the occurence of quark matter in
compact stars is excluded as well [3]. In the present contribution it is shown that within modern
quantum field theoretical approaches to quark matter [4] including color superconductivity and a
vector mean field allow a microscopic description of hybrid stars which fulfill the new, strong
constraints. For these objects color superconductivity turns out to be essential for a successful
description of the cooling phenomenology in accordance with recently developed tests [5].
Implications for the QCD phase diagram to be explored in future generations of nucleus-nucleus
collision experiments at low temperatures and high baryon densities such as CBM @ FAIR are
presented.
References
[1] T. KlÄhn et al., arXiv:nucl-th/0602038.
[2] F. özel, Nature 441, 1115 (2006)
[3] M. Alford et al., arXiv:astro-ph/0606524.
[4] D. Blaschke et al., Phys. Rev. D 72 (2005) 065020
[5] S. Popov et al., Phys. Rev. C 74 (2006) in press; [arXiv:nucl-th/0512098].
IX.
New Theoretical Developments
247.
Thermalization of Quark-Gluon Matter
Xiao-Ming Xu a
Department of Physics, Shanghai University
Baoshan, Shanghai, 200444, P. R. China, [email protected]
a
Rapid thermalization needs to be understood in QCD. The 2→2 parton scatterings and gg→ggg
inelastic scatterings contribute to the thermalization process [1-4]. Respecting high gluon number
density produced in initial Au-Au collisions at RHIC, ggg→ggg elastic scatterings occur and are
shown to be important in shortening thermalization time [5]. Both gg→gg and ggg→ggg elastic
scatterings lead to a thermalization time of the order of 0.45 fm/c. The study of rapid thermalization
can reveal important processes that take place at high gluon number density.
The method for studying thermalization of quark-gluon matter is based on transport equations
of Boltzmann type. The gauge-invariant squared amplitudes for the 3→3 elastic scatterings form
new terms in the transport equations. However, the squared amplitudes involve a great many
interference terms of Feynman diagrams. This renders that the calculation of squared amplitudes in
perturbative QCD is a cumbersome task. Anisotropic parton distribution created in initial Au-Au
collisions is used as an input. Solutions of transport equations show that momentum isotropy can be
established by 2→2 and 3→3 elastic scatterings and a thermal state is attained.
The study of quark-matter and antiquark-matter thermalization is more complicated than
gluon-matter thermalization because different flavors and antiquarks are involved. The qqq→ qqq
and qq→qq elastic scatterings lead to a thermalization time of the order of 1.8 fm/c [6]. qq q →qq q
and q q q →q q q elastic scatterings can shorten thermalization time by 0.25 fm/c if we assume that
121
the four distributions of up-quark, down-quark, up-antiquark and down-antiquark are the same.
Rapid thermalization of quark matter and antiquark matter still waits to be understood.
References:
[1] E. Shuryak, Physical Review Letters, 68, 3270, 1992.
[2] K. Geiger, Physical Review, D46, 4965, 1992; D46, 4986, 1992.
[3] G.R. Shin, and B. MÄuller, Journal of Physics, G29, 2485, 2003.
[4] Z. Xu, and C. Greiner, Physical Review, C71, 064901, 2005.
[5] X.-M. Xu, Y. Sun, A.-Q. Chen, and L. Zheng, Nuclear Physics, A744, 347, 2004.
[6] X.-M. Xu, R. Peng, and H.J. Weber, Physics Letters, B629, 68, 2005.
248.
Micro-canonical pentaquark production in e+e- annihilations and pp collisions
Fu-Ming Liu
[email protected]
Institute of Particle Physics, Central China Normal University, Wuhan, China
Klaus Werner
Laboratoire SUBATECH, University of Nantes - IN2P3/CNRS - Ecole des Mines de Nantes, Nantes,
France
The existence of pentaquarks, namely baryonic states made up of four quarks and one antiquark,
became questionable, because the candidates, i.e. the Θ+ peak, are seen in certain reactions, i.e. p+p
collisions, but not in others, i.e. e+e- annihilations. In this paper, we estimate the production of
Θ+(1540) and Ξ--(1860) in e+e- annihilations at different energies using Fermi statistical model as
originally proposed in its microcanonical form. The results is compared with that from pp collisions
at SPS and RHIC energies. We find that, if pentaquark states exist, the production is highly possible
in e+e- annihilations. For example, at LEP energy s =91.2GeV, bothΘ+(1540)andΞ--(1860) yield more than in pp collisions at SPS and RHIC energy. References: [1] Sonia Kabana, J. Phys. G 31, (2005), S1155-S1164. [2] F.M. Liu, H. Stoecker, K. Werner, Phys. Lett. B 597 (2004)333-337. F.M.Liu, K.Werner,hep-ph/0507051. [3] F. Becattini and U. Heinz Z.Phys. C76 (1997) 269. F. Becattini, hep-ph/9701275 [4] K. Werner and J. Aichelin, Phys. Rev. C 52 (1995) 1584-1603. [5] F.M.Liu, K.Werner and J.Aichelin, Phys. Rev. C 68, (2003) 024905. 249. BOUND QUARKONIA IN QUARK-GLUON PLASMA Cheuk-Yin Wong Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831 U.S.A. [email protected] Physics Department, University of Tennessee, Knoxville, TN, 37996 U.S.A. The successes of the recombination models suggest the possibility that quark partons may form bound or quasi-bound states in the quark-gluon plasma. Furthermore, the successes of the hadron yield thermal models raise the question whether quarkonium chemical equilibration commences already in the late QGP phase to reach hadron chemical equilibrium very close to the QGP phase boundary. It is therefore of great interest to study the stability of quarkonia in quark-gluon plasma. The potential U Q1Q ( R) that appears in the color-singlet Q  Q Schrödinger equation contains those interactions that act on Q and Q , when the QGP medium particles have re-arranged themselves self-consistently. As shown theoretically in detail in Ref[1] for lattice gauge theory and supported explicitly in the analogous case of Debye screening in Ref.[2], this potential is given by U 1 ( R)  [U g ( R)  U g 0 ] , where U 1 is the color-singlet internal energy, U g ( R, T ) and U g 0 are gluon internal energy in the presence and absence of Q and Q , respectively. We can use the quark-gluon plasma equation of state to express [U g ( R)  U g 0 ] in terms of the gluon entropy, 122 which has been calculated as U 1 minus the free energy F1. The color-singlet Q  Q potential then becomes [1,2] 3 a(T ) U Q(1Q) ( R)  F1 ( R)  U 1 ( R), 3  a(T ) 3  a(T ) where a(T )  3 p(T ) /  (T ) is given by the equation of state. Using F1, U1 and a (T ) obtained in lattice gauge calculations [3,4], the potential is tested and found to give dissociation temperatures that agree well with those from lattice gauge spectral function analysis. To examine the stability of quarkonia, we consider the quark mass mQ as a variable and evaluate the spontaneous dissociation temperature as a function of the reduced mass  red  mQ mQ /( mQ  mQ ) . The results are expressed in the T ,  red  plane as the quark drip lines shown in the above figure. A quarkonium is bound in the T ,  red  space above a drip line and is unbound below the drip line. Various estimates give an effective light quark mass of 300-400 MeV [5] which will imply from the above figure that quarkonia of light quarks would be stable in the quark gluon plasma up to a temperature just slightly above the QGP phase transition temperature. References [1] C. Y. Wong, Phys. Rev. {\bf C72}, 034906 (2005). [2] C. Y. Wong, hep-ph/0606200. [3] O. Kaczmarek et~al. hep-lat/0309121; O. Kaczmarek and F. Zantow, Phys. Rev. D71, 114510 (2005), and O. Kaczmarek and F. Zantow, hep-lat/0506019. [4] G.Boyd et~al.,Nucl.Phys.B 469, 419 (1996); F.Karsch, E.Laermann, and A.Peikert,Phys.Lett.B478,447(2000). [5] P. Levai and U. Heinz, Phys. Rev. 57, 1879 (1998). 250. Susceptibilities and the Phase Structure of a Chiral Model with the Polyakov Loop 1 C. Sasakia, B. Frimana and K. Redlichb fÄur Schwerionenforschung (GSI),64291 Darmstadt, Germany, [email protected], [email protected] bInstitute of Theoretical Physics, University of Wroclaw, PL{50204 WrocÃlaw, Poland, [email protected] aGesellschaft Low-energy phenomena of QCD have been studied in various effective models based on chiral symmetry. However, the relation of spontaneous chiral symmetry breaking and confinement remains an open issue. In order to obtain a unified picture of these phenomena, several effective chiral models based on an extension of the Nambu--Jona-Lasinio (NJL) model~[2,3] have been proposed and developed~[4]. The basic ingredients of the model are constituent quarks and the Polyakov loop, which is an order parameter of the Z(3) symmetry of QCD in the heavy quark limit. The model has a non-vanishing coupling of the constituent quarks to the Polyakov loop and mimics confinement in the sense that only three-quark states contribute to the thermodynamics in the low-temperature phase. We explore the NJL model with Polyakov loops for a system of three colors and two flavors within the mean-field approximation, where both chiral symmetry and confinement are taken into account. In the chiral limit the phase diagram of these models exhibit a tricritical point, the end point of the first order phase transition. We focus on the phase structure of the model and study the chiral and Polyakov loop susceptibilities. References: [1] C. Sasaki, B. Friman and K. Redlich, to appear. [2] Y. Nambu and G. Jona-Lasinio, Phys. Rev. 122, 345 (1961); Phys. Rev. 124, 246(1961). [3] For reviews, see e.g., U. Vogl and W. Weise, Prog. Part. Nucl. Phys. 27, 195 (1991);S. P. Klevansky, Rev. 123 Mod. Phys. 64 649 (1992); T. Hatsuda and T. Kunihiro, Phys.Rept. 247, 221 (1994); M. Buballa, Phys. Rept. 407, 205 (2005). [4] P. N. Meisinger and M. C. Ogilvie, Phys. Lett. B 379, 163 (1996); P. N. Meisinger,T. R. Miller and M. C. Ogilvie, Phys. Rev. D 65, 034009 (2002); K. Fukushima, Phys.Lett. B 591, 277 (2004); C. Ratti, M. A. Thaler and W. Weise, Phys. Rev. D 73,014019 (2006). 1 Based on the work done in Ref. [1]. 251. Dissipative hydrodynamics in 2+1 dimensions A. K. Chaudhuri Variable Energy Cyclotron Centrem1-AF, Bidhan Nagar, Kolkata 700 064, India, [email protected] In 2+1 dimensions, we have simulated the hydrodynamic evolution of QGP fluid with dissipation due to shear viscosity [1]. Comparison of evolution of ideal and viscous fluid, both initialized under the same conditions e.g. same equilibration time, energy density and velocity profile, reveal that the dissipative fluid evolves slowly, cooling at a slower rate. Cooling get still slower for higher viscosity. The fluid velocities on the otherhand evolve faster in a dissipative fluid than in an ideal fluid. The transverse expansion is also enhanced in dissipative evolution. For the same decoupling temperature, freeze-out surface for a dissipative fluid is more extended than an ideal fluid. Dissipation produces entropy as a result of which particle production is increased. Particle production is increased due to (i) extension of the freeze-out surface and (ii) change of the equilibrium distribution function to a non-equilibrium one, the last effect being prominent at large transverse momentum. Compared to ideal fluid, transverse momentum distribution of pion production is considerably enhanced. Enhancement is more at high pT than at low pT . Pion production also increases with viscosity, larger the viscosity, more is the pion production. Dissipation also modifies the elliptic flow. Elliptic flow is reduced in viscous dynamics. Also, contrary to ideal dynamics where elliptic flow continues to increase with transverse momentum, in viscous dynamics, elliptic flow tends to saturate at large transverse momentum. The analysis suggest that initial conditions of the hot, dense matter produced in Au+Au collisions at RHIC, as extracted from ideal fluid analysis can be changed significantly if the QGP fluid is viscous. References: 1. A. K. Chaudhuri, nucl-th/0604014 . 252. CHROMO-HYDRODYNAMICS OF THE UNSTABLE QUARK-GLUON PLASMA Stanisław Mrówczyński Institute of Physics, Świętokrzyska Academy ul. Świętokrzyska 15, PL - 25-406 Kielce, Poland and So ltan Institute for Nuclear Studies, This contribution is based on the article prepared in collaboration with Cristina Manuel [1]. We derive hydrodynamic-like equations that are applicable to short-time scale color phenomena in the quark-gluon plasma. The equations are solved in the linear response approximation, and the gluon polarization tensor is derived. As an application, we study the collective modes in a two-stream system and find plasma instabilities when the fluid velocity is larger than the speed of sound in the plasma. The chromo-hydrodynamic approach, to be discussed in detail, should be considered as simpler over other approaches and well-designed for numerical studies of the dynamics of an unstable quark-gluon plasma. References [1] C. Manuel and St. Mr´owczy´nski, Chromo-hydrodynamic approach to the unstable quarkgluon plasma, arXiv:hep-ph/0606276. 253. QGP correlations and phases of many-particle amplitudes aLebedev I.M. Dremina Physical Institute, Moscow, 119991, Russia, [email protected] 124 The oscillations of cumulant moments of multiplicity distributions indicate the important role of phases of many-particle amplitudes. The simple model is proposed to demonstrate how these oscillations are related to signs of the cut irreducible many-particle amplitudes. The relation between oscillations in AA, pA, pp, ep, ee processes is discussed. 254. The Statistical Model and Different Freeze-Out Conditions H. Oeschlera, J. Cleymansb, K. Redlichc and S. Wheatona;b Institute of Nuclear Physics, Technische Universität Darmstadt, D-64289 Darmstadt, Germany, [email protected] b UCT-CERN Research Centre and Department of Physics, University of Cape Town, Rondebosch 7701, South Africa c Institute of Theoretical Physics, University of WrocÃlaw,Pl-45204 WrocÃlaw, Poland a The recently discovered sharp peak in the excitation function of the K+/   ratio around 30 A GeV in relativistic heavy-ion collisions is discussed in the framework of the Statistical Model [1]. In this model, the freeze-out of an ideal hadron gas changes at a temperature T = 140 MeV and a baryon chemical potential  B = 410 MeV corresponding to an energy of s NN = 8.2 GeV, from a situation where baryons dominate to one with mainly mesons [2]. The calculated maximum in the excitation function of the K+/   ratio is, however, much less pronounced than the one observed by the NA49 Collaboration [3]. The smooth increase of the K-/   ratio with incident energy showing no maximum and the various shapes of the excitation functions of the  /   ,   /   ,   /   ratios, all exhibiting maxima at different incident energies, are consistent with the presently available experimental data. The measured K+/   ratio exceeds the calculated one just at the incident energy when the freeze-out condition is changing. We speculate that at this point chemical freeze-out might occur in a modified way. We discuss a scenario of an early freeze-out happening just in this energy regime. This would indeed increases K+/   ratio while most other particle ratios remain essentially unchanged [4]. Such an early freeze-out is supported by results from HBT studies [5]. References [1] P. Braun-Munzinger, J. Cleymans, H. Oeschler, K. Redlich, Nucl. Phys. A 697, p. 902-912, 2002. [2] J. Cleymans, H. Oeschler, K. Redlich, S. Wheaton, Phys. Lett. B 615, p. 50-54, 2005. [3] C. Blume, (NA49 Collaboration), J. Phys. G: Nucl. Part. Phys. 33, p. S685 -S691,2005. [4] S. Wheaton, Ph.D. thesis, University of Cape Town, 2005. [5] D. Adamova et al., (CERES Collaboration), Phys. Rev. Lett. 90, p. 022301, 2003. 255. EARLY TIME EVOLUTION OF HIGH ENERGY HEAVY ION COLLISIONS R. J. Friesa, J. I. Kapustab and Y. Lic of Physics and Astronomy, University of Minnesota Minneapolis, MN, 55455, USA, [email protected] bSchool of Physics and Astronomy, University of Minnesota Minneapolis, MN, 55455, USA, [email protected] cSchool of Physics and Astronomy, University of Minnesota Minneapolis, MN, 55455, USA, [email protected] aSchool We present a model for the early time evolution of a relativistic heavy ion collision. We suggest a near-_eld expansion of the classical gluon _eld in the framework of the McLerran-Venugopalan model. The evolution of the energy momentum tensor at early times is computed. The sources of the classical _elds are modeled using parton distributions and coarse graining methods. Assuming rapid thermalization we derive constraints on the energy density, pressure and ow of the subsequent thermalized plasma phase. Our results can be used as initial conditions for a further hydrodynamic evolution. 256. 125 What can we learn from the AdS/CFT correspondence about heavy ion phenomenology? a Urs Achim Wiedemanna Department of Physics, CERN, Theory Division,CH-1211 Geneve 23, [email protected] The calculation of processes in a finite temperature environment at non-perturbatively strong coupling is of particular interest for heavy ion collisions at collider energies. For many of the processes under active study, such as jet quenching and collective flow, the understanding of real-time dynamics appears to be as important as that of equilibrium physics. Lattice QCD, the prime source of rigorous non-perturbative information in heavy ion physics, is formulated in Euclidean space and thus less suited to address problems involving real-time dynamics. Complementary approaches are desirable. The AdS/CFT conjecture gives analytically access to the strong coupling regime of finite temperature gauge field theories by mapping non-perturbative problems onto calculable problems in a dual supergravity theory. It allows for the formulation of problems involving real time dynamics. On the other hand, the AdS/CFT conjecture is at present limited to a class of supersymmetric quantum field theories; these theories share in the high temperature sector many properties with QCD. In this talk, I discuss recent progress in applying the AdS/CFT correspondence to problems of central importance in heavy ion physics. The focus will be in particular on problems involving real-time dynamics. References [1] H. Liu, K. Rajagopal and U. A. Wiedemann, An AdS/CFT calculation of screening in a hot wind, arXiv:hep-ph/0607062. [2] H. Liu, K. Rajagopal and U. A. Wiedemann, Calculating the jet quenching parameter from AdS/CFT, arXiv:hep-ph/0605178. 257. SPACE-TIME EVOLUTION OF A CHEMICALLY EQUILIBRATING QGP AT FINITE BARYON DENSITY Z.J.Hea, J.L.Longa and Y.G.Maa Institute of Applied Physics, Chinese Academy of Sciences Shanghai, 201800, P. R. China, [email protected] aShanghai During past twenty years, hydrodynamics proved to be quite a reasonable tool for describing heavy-ion collisions at moderate energies [1]. In our work, we have developed a relativistic 3+1D hydrodynamic model for describing heavy-ion collisions at RHIC energies. We treated the quark-gluon plasma as a chemically equilibrating system with ¯nite baryon density. We derived a set of relaxation equations characterizing the chemical equilibration of gluons, quarks and s quarks, which is established based on the JÄuttner distribution function of partons of the system. Under initial values obtained by the self-screened cascade(SSPC) model we solved the set of relaxation equations, and then we got the space-time(3+1D) evolution of the system. References [1] V.D. Toneev et al. e-print Arxiv: nucl-th/0309008. 258. Amplification of Quantum Meson Modes in the Late Time of the Chiral Phase Transition K. Watanabea and Y. Tsueb Junior High School, Kochi Gakuen,Kochi 780-0956, Japan, [email protected] bPhysics Division, Faculty of Science, Kochi University,Kochi 780-8520, Japan, [email protected] aKochi One of the recent interests in the context of the relativistic heavy ion collisions is to clarify the nature of matter at very high energy density. Especially, it is interested in the dynamics of the chiral condensate and quantum meson modes around it in the chiral phase transition. We use the variational approach to the O(4) linear sigma model in the Gaussian wave functional approximation [1, 2]. In this paper, it is pointed out that there is a possibility of amplification of amplitudes of quantum pion modes with low momenta even in the late time of chiral phase transition [3]. It is shown that the amplification occurs in the mechanism of the resonance by forced oscillation as well as the parametric resonance induced by the small oscillation of the chiral condensate. This means 126 that the equation of motion for the amplitudes of quantum meson mode, u~ ka (t ) , can be expressed as following form, d2 1 [ 2  2 [1  h cos(t )]]u~ ka (t )  F cos(t )e i t dt Here, this equation is derived by using the solution of equation for the chiral condensate. The variables  , h and F are written in terms of the model parameters in the O(4) linear sigma model. If F is negligible, then Eq. (1) is reduced to Mathieu's equation. In this case, the existence of the unstable solution for u~ k (t ) may be expected. This phenomenon is well known as a parametric resonance in classical mechanics. On the other hand, forced oscillation may be realized through the effect of F , even if the model parameters do not allow for unstable regions for the parametric resonance. The unstable regions are given for quantum meson modes, which lead to the emission of quantum mesons. Furthermore, the momentum distribution of the emitted pions is calculated at each time. References [1] D. Vautherin and T. Matsui, Phys. Rev. D 55 (1997), 4492. D. Vautherin and T. Matsui, Phys. Lett. B 437 (1998), 137. [2] Y. Tsue, D. Vautherin and T. Matsui, Prog. Theor. Phys. 102 (1999), 313. Y. Tsue, D. Vautherin and T. Matsui, Phys. Rev. D 61 (2000), 076006. [3] K. Watanabe, Y. Tsue and S. Nishiyama, Prog. Theor. Phys. 113 (2005), 369. 259. MAGNETIC INSTABILITY OF QUARK MATTER T. Tatsumi Department of Physics, Kyoto University, Kyoto 606-8502, Japan, [email protected],jp We have discussed a possibility of spontaneous spin polarization (ferromagnetism) in quark matter at low temperature [1]. In this talk we present a new approach to examine it. Using Landau Fermi-liquid theory we caiculate the magnetic susceptibility of quark matter within one-gluon-exchange interaction. Specifing the spin polarization of each quark by introducing the spin vector aμ, which is a covariant generalization of the spin direction ζ (along z- axis) in the nonrelativistic case [1], we can derive the Fermi-liquid interaction by the one gluon exchange interaction, 1 f kζζqζ | k  q k  f k,q | k  q k F ζζ f k, q | k  q k F , as a sum of spin-independent and -dependent pieces. Since the exchanged gluon is soft, we must modify the gluon propagator by doing the high-density loop (HDL) resummation [2]. Thus we take into account the Debye screening for the longitudinal gluons but still no screening for transverse gluons. We obtain the magnetic susceptibility by appling a vanishingly small magnetic field, and evaluating the magnetization <M>, which is given by the difference of the number of the quasiparticles with different spins. The magnetic susceptibility χ for a given Fermi momentum kF is then evaluated as M  2 1  | N ,T  ( g D  q / 2) 2 [  f1  f 0]1 B NC N F kF  3 within Fermi-liquid theory, where f l ( f l) denotes a l−th coefficient of the Legendre expansion of the Fermi-liquid interaction (1), and μq and gD are Dirac manetic moment and the gyromagnetic ratio, respectively. We can show that it is independent of the gauge choice, as should be [3]. When we depict χ as a function of kF , we can see that it diverges at two 127 critical values, kF cH and kF cL; the latter is a usual one and also seen for the electron gas, while the former is novel and given by a relativistic effect due to the screening. An implication of ferromagnetism on compact stars, especially magnetars, is briefly discussed. References [1] T. Tatsumi, Phys. Lett. B, v.489, p.280, 2000:E. Nakano et al., Phys. Rev. D, v.68, p.105001, 2003; T. Tatsumi et al., Prog. Theor. Phys. Suppl., v.153, p.190, 2004; T. Tatsumi et al., in Dark matter,NOVA pub., 2005. [2] T. Scha¨afer and F. Wilczeck, Phys. Rev. D, v.60, p.114033, 1999. [3] T. Tatsumi, in preparation. 260. Oscillating Correlation Function in QGP Hui Liua and Jia-rong Lib Institute of Particle Physics, Central China Normal University Wuhan 430079, P. R. China, [email protected] b Institute of Particle Physics, Central China Normal University Wuhan 430079, P. R. China, [email protected] a It was believed that quarks in the hadrons are to be deconfined in the high temperature environment so as to form the weakly coupled quark-gluon plasma (QGP)in heavy ion collision. However recent research on RHIC physics shows that the hot/dense medium produced in the collision behaves like an almost perfect fluid and might be strongly coupled or correlated. This phenomenon is expected to be understood with the existence of a long distance oscillating potential, like what happened in the liquid state[1,2]. While the formation of this oscillating potential is not clear so far. In this work, we present a mechanism of forming such a long distance screen potential which results in the liquid-like correlation function.At the temperature slightly above the critical point, based on the scenario of strong coupled bound state background Coulomb field we propose an ansatz of a physical propagator to obtain the color charge correlation between two bound states through calculating color dielectric function. We find out that the screen potential exhibits a long oscillating tail at large distance in the non-static limit, i.e., the momentum transfer between quark and gluon is not vanishing. The reason for the existence of such an oscillating correlation is owing to the singular behavior of the color dynamical dielectric function around the 2 m 2 [3,4], where m 2 is the effective mass of quark modified by the medium effect. This calculation provides a dynamics explanation for the oscillating potential required by the ideal fluid performance. References [1] B.A. Gelman, E.V. Shuryak and I. Zahed, arXiv:hep-th/0601029 [2] M.H. Thoma, J. Phys. G, Nucl. Part. Phys. 31, No. 1(Jan.2005) L7-L12 [3] H. Liu and J.-R. Li, Phys. Rev. C 69, 037601(2004) [4] H. Liu and J.-R. Li, Mod. Phys. Lett. A, Vol.19, No.11,855(2004) 261. Jet-fluid string formation and decay in high-energy heavy-ion collisions M. Issea, T. Hiranob, Y. Narac, A. Ohnishid, K. Yoshinod Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan, [email protected] b Institute of Physics, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Tokyo 153-8902, Japan, [email protected] c Institut fu¨r Theoretische Physik, Johann Wolfgang Goethe-Universit¨at, 60438 Frankfurt am Main, Germany, [email protected] d Division of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan, [email protected], [email protected] a One of the most intriguing findings at RHIC is suppression of hadron yield in high pT regions. Nowadays, this is commonly believed to be a direct consequence of parton energy loss in the dense deconfined matter. However, momentum anisotropy, v2, is not well understood yet in the high pT region: most theoretical results are smaller than experimental data. One may obtain a larger v2 by assuming a sharper density profile for produced matter compared to Woods-Saxon type density distribution[1]. However, large eccentricity from a sharp density profile would spoil an agreement 128 of hydrodynamic predictions with v2 data in low pT regions. In this study, we propose a new model for hadronization, the jet-fluid string (JFS) model, to understand observables in intermediate to high pT regions comprehensively. Production of hard partons are estimated by utilizing PYTHIA [2]. These hard partons lose their energy in traversing the QGP phase according to the Gyulassy-L´evai-Vitev formula [3]. At the same time, space-time evolution of the QGP is described by fully three-dimensional hydrodynamic simulations [4]. When a jet parton escapes from the QGP phase, it picks up a partner parton from a fluid to form a hadronic string. We evaluate hadron pT spectra and v2 from decay of these JFSs which is simulated by the Lund fragmentation scheme in PYTHIA [2]. We will also show that this hadronization mechanism gives a jet-like structure in azimuthal correlation functions, dN/d∆φ, in intermediate to high pT regions. References: [1] J. Adams et al. [STAR Collaboration], Phys. Rev. Lett. 93, 252301 (2004). [2] T. Sj¨ostrand et al., Comp. Phys. Comm. 135, 238 (2001). [3] M. Gyulassy, P. L´evai and I. Vitev, Nucl. Phys. B594, 371 (2001); B571, 197 (2000); Phys. Rev. Lett. 85, 5535 (2000). [4] T. Hirano and Y. Nara, Phys. Rev. C 69, 034908 (2004). 262. Analysis of large transverse momentum distributions by relativistic diffusion model N. Suzukia and M. BIyajimab of Comprehensive Management, Matsumoto University Matsumoto 390-1295, Japan, [email protected] bDepartment of Physics, Shinshu University, Matsumoto, 390-8621, Japan, [email protected] aDepartment In order to describe large transverse momentum (pT ) distributions observed in high energy hadron-hadron or nucleus-nucleus collisions, a stochastic model in the three dimensional rapidity space is introduced. The fundamental solution of the radial symmetric diffuison equation is Gaussian-like in radial rapidity. We can also derive a pT or radial rapidity distribution function, where radial flow is taken into account. The solution is applied to to the analysis of observed large pT distributions of charged particles. For simplicity, we consider the diffusion equation with radial symmetry in the geodesic polar coordinate system, with an initial condition where, ρ denotes the radial rapidity, which is written with energy E, momentum p and mass m of observed particle, ρ = ln(E + |p|)/m. The solution is given by where ρ0 denotes the radial rapidity of an emission center. It would be identified to the radial flow rapidity. We can analyze large transverse momentum distributions observed at RHIC including flow effect by the this equation. References: [1] N. Suzuki and M. Biyajima, XXXV International symposium on multiparticle dynamics , Kromeriz, Chech republic 9-15 August 2005, eds. V.Simak et al, American Institute of Physics, p.257-262, 2006 263. Unconventional color superconductor: beyond standard BCS theory 129 Mei Huanga Division, Institute of High Energy Physics, Chinese Academy of Sciences Beijing 100039, P. R. China, [email protected] aTheory Superfluidity or superconductivity with mismatched Fermi momenta appears in many sys- tems such as the charge neutral dense quark matter, the asymmetric nuclear matter, and in imbalanced cold atomic gases. The mismatch plays the role of breaking the Cooper pairing, and the pair-breaking state cannot be properly described in the framework of standard BCS theory. I will review recent theoretical development in understanding unconventional color superconductivity, including gapless color superconductor, the chromomagnetic instabilities and the Higgs instability in the gapless phase. I will introduce a possible new framework for describing unconventional color superconductor. References: [1] M. Huang, P. F. Zhuang and W. Q. Chao, Phys. Rev. D 67, 065015 (2003); I. Shovkovy and M. Huang, Phys. Lett. B 564, 205 (2003); M. Huang and I. Shovkovy, Nucl. Phys. A729, 835 (2003). [2] M. Huang and I. A. Shovkovy, Phys. Rev. D 70, 051501 (2004); M. Huang and I. A. Shovkovy, Phys. Rev. D 70, 094030 (2004). [3] Mei Huang, Int. J. Mod. Phys. A 21, 910 (2006); Mei Huang, Phys. Rev. D 73, 045007 (2006). [4] I. Giannakis, D. Hou, M. Huang and H. c. Ren, hep-ph/0606178. 264. HYPERON POLARIZATION IN QUARK-DIQUARK CASCADE MODEL T. Tashiroa, H. Nodab, S. Nakarikia and K. Fukumac of Computer Simulation, Okayama University of Science Ridai-cho, Okayama, 700-0005, Japan, [email protected], [email protected], bDepartment of Mathematical Science, Ibaraki University Bunkyou, Mito, 310-8512, Japan, [email protected] cDepartment of Control Engineering, Takuma National College of Technology Mitoyo, Kagawa, 769-1192, Japan, [email protected] aDepartment It is well known that leading hyperons produced in unpolarized proton-proton and protonnucleus collisions are polarized transversely to the production plane of the hyperon and various models have been proposed [1]. In the forward hadron production, the valence quark in the projectile plays an important role. We discuss the polarization of inclusively produced hyperons in the framework of the constituent quark-diquark cascade model with SU(6) wave functions for hadrons. The hyperon polarizations in unpolarized reactions are explained by relating them to leftright asymmetries in singly polarized reactions [2]. Following this idea we assume that, when a leading baryon is produced, the spin up valence quark in the projectile is preferentially chosen as compared to the spin down valence quark by a sea diquark. The process q↓ v+qqsjz →Bjz −1/2 is related to the process q↓ s + qqvjz→ Bjz −1/2 by interchanging the roles of valence and sea quarks. Since the normal to the production plane of the leading baryon valence quark qqv is opposite to that of B from the valence quark qv, this process should be read as We assume that the valence diquark in the incident nucleon tends to combine with a spin down sea quark. These assumptions, with Glauber model for proton-nucleus collisions, explain the various experimental data on the hyperon polarizations in hadronic interactions. Although, there are some discrepancies between the results of our model and the experimental data such as the Λ polarization in Σ− fragmentation region [3] , the hyperon polarizaion in pA and K −p collisions are well explained. We are investigating the strangeness transfer and annihilation effects. References: [1] For reviews, see for example, J. Soffer: hep-ph/9911373; V.V. Abramov: hep-ph/0111128. [2] C. Boros, Liang Zuo-tang: Phys. Rev. D53, R2279(1996); Liang Zuo-tang, C. Boros: Phys. Rev. D79, 3608 (1997); Dong Hui, Liang Zuo-tang: Phys. Rev. D70, 014019(2004) [3] M.I. Adamovich et al.: Eur. Phys. J. C32, 221(2004) 265. 130 A CALCULATION OF TRANSPORT COEFFICIENTS OF RELATIVISTIC DISSIPATIVE HYDRODYNAMICS FOR A HADRONIC FLUID S. Muroya Department of CM, Matsumoto University Matsumoto, Nagano 390-1295, Japan, [email protected] In this paper we investigate transport coefficients in a relativistic dissipative hydrodynamics of a hadronic gas.Using a Monte Carlo hadronic collision event generator URASiMA, we have already discussed thermodynamical quantities and viscosities of a hadronic gas. Shear viscosity to entropy density ratio is, for example, evaluated and it is approximately 0.3 – 0.6 in the range T =100 – 180MeV and is quite insensitive to the baryon number density[1]. Relativistic causal dissipative hydrodynamics is known to contain several additional coeffi- cients other than ordinary transport coefficients, heat conductivity, shear viscosity and bulk viscosity. In this paper, we calculate both ordinary transport coefficients and new coefficients based on a microscopic picture by using URASiMA, and investigate how important these quantities are for the space time evolution of a hot fluid produced in RHIC. References: [1] Shin Muroya and Nobuo Sasaki, Progress of Theoretical Physics , v. 113, p. 457-462, 2005. 266. ELECTROMAGNETIC RADIATION FROM BROKEN SYMMETRIES IN RELATIVISTIC NUCLEAR COLLISIONS G. Qina, C. Galea, and A. Majumderb of Physics, McGill University,Montreal, QC, H3A 2T8, Canada [email protected] bDepartment of Physics, Duke University,Durham, NC 27708-03051, USA [email protected] aDepartment In a medium where charge conjugation symmetry is spontaneously broken, processes that are usually forbidden because of Furry’s theorem can occur. Consequently, in a hot plasma containing a residual charge density, processes that contain a virtual quark (antiquark) loop like gluon fusion and decay may now proceed with a lepton pair or real photon signature. We investigate those in Hard Thermal Loop effective theory and point out their observable properties at RHIC and at the LHC. In particular, we investigate the sensitivity of the channels to departures from chemical equilibrium at early times and high temperatures. Similarly, the situation where one of the initial state partons is a hard QCD jet is considered, together with its electromagnetic signature. It is found that in some regions of phase space, the new processes outshine those associated with the leading order term. References: [1] A. Majumder, A. Bourque, and C. Gale, Phys. Rev. C 69, 064901 (2004). [2] G. Qin, A. Majumder, and C. Gale, to be submitted (2006). 267. JET-PLASMA INTERACTIONS AND THEIR ELECTROMAGNETIC SIGNATURE C. Gale and S. Turbide Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada [email protected] At RHIC, the suppression of jets constitutes one of the most spectacular measurements of relativistic heavy ion physics. In this talk, we interpret this experimental result within a finite-temperature field theory formalism, and using the same approach we estimate the electromagnetic radiation being generated as a consequence of jet-plasma interactions. We show that the recent photon data from the PHENIX collaboration can be interpreted in terms of this novel mechanism, which also involves jet energy-loss. We show how the jet- plasma radiation can be isolated directly through measurements of the photon and dilepton azimuthal anisotropy, including also the effect of hydrodynamic flow. We make predictions for LHC energies. References: [1] S. Turbide, C. Gale, S. Jeon, and G. D. Moore, Phys. Rev. C 72, 014906 (2005). [2] S. Turbide, C. Gale, and R. Fries, Phys. Rev. Lett. 96, 032303 (2006). 131 268. All orders Boltzmann collision term from the multiple scattering expansion of self-energy S. Jeona,b, F. Fillion-Gourdeaua, and J.S. Gagnona Department of Physics, McGill University,Montreal, Quebec, H3A-2T8, CANADA, [email protected] b The presenting author. a Starting from the Kadanoff-Baym relativistic transport equation and the multiple scattering expansion of the self-energy, we obtain the Boltzmann collision terms for any number of participating particles to all orders in perturbation theory within a quasi-particle approximation. In this talk, emphasis will be on identifying the various approximations that are needed to get to the final form and the region of validity for each approximation. References: [1]F. Fillion-Gourdeau, J. S. Gagnon and S. Jeon, All orders Boltzmann collision term from the multiple scattering expansion of the self-energy, ,Phys. Rev. D 74, 025010 (2006). 269. Collective excitations of quarks near chiral transition at finite temperature Y. Nemotoa, M. Kitazawab and T. Kunihiroc of Physics, Nagoya University,Nagoya, Aichi, 464-8602, Japan, [email protected] bRIKEN-BNL Research Center,Brookhaven National Laboratory, Upton, NY, 11973, USA cYukawa Institute for Theoretical Physics, Kyoto University,Kyoto, Kyoto, 606-8502, Japan aDepartment We investigate the quasi-quark spectrum near but above the chiral transition at finite temperature, focusing on the effects of the precursory hadronic soft modes of the phase transition on the quark spectrum. It is found that there appear novel excitation spectra of quasi-quarks and quasi-antiquarks with a three-peak structure[1]. We show that the new spectra originate from the mixing between a quark (anti-quark) and an anti-quark hole (quark hole) in the thermally-excited anti-quark (quark) distribution; the mixing can be interpreted in terms of a “resonant scattering” of the quasi-quarks with the thermally-excited soft modes which have a small but finite excitation energy at zero momentum. This is contrasted to the case of (color-)superconducting transition around the Fermi surface[2,3]. It is also shown that such a spectrum can be seen in a massless fermion spectrum coupled to a massive scalar boson via the Yukawa coupling at finite temperature. It is found that there appears a three-peak structure of the fermion spectrum at intermediate temperatures. While two peaks of them in the high temperature limit approach the quasi-quark and the plasmino obtained in the hard thermal loop approximation, the other peak which appears around the origin in the phase space appears only at intermediate temperature at the same order of the boson mass. We discuss the origin of these peaks with the self-energy of the fermion and show that the Landau damping processes mix the fermion (anti-fermion) and the anti-fermion hole (fermion hole) states and then cause the resonant scattering of the fermion with the boson, leading to the three-peak structure of the spectral function. We also show that a similar three-peak spectrum appears if a massive vector boson is coupled instead of the scalar boson. These results indicate that the quark spectrum might show several collective excitation modes in the QGP phase, if there exist any bosonic excitations whose excitation energy is at the same order of temperature. References: [1] M. Kitazawa, T. Kunihiro and Y. Nemoto, Phys. Lett. B 633, 269 (2006). [2] M. Kitazawa, T. Kunihiro and Y. Nemoto, Phys. Lett. B 631, 157 (2005). [3] M. Kitazawa, T. Koide, T. Kunihiro and Y. Nemoto, Prog. Theor. Phys. 114, 117 (2005). 270. From RHIC to LHC: A relativistic diffusion approach G. Wolschin 132 Philosophenweg 16, D-69120 Heidelberg, Germany, [email protected] Stopping and particle production in heavy-ion collisions are investigated in a Relativistic Diffusion Model (RDM) [1,2]. Using three sources for particle production, the energy- and centrality-dependence of rapidity distributions of net protons, and pseudorapidity distri- butions of charged hadrons [3,4] in heavy systems at RHIC energies are precisely reproduced in the analytical model. The distribution functions Rk(y,t) for the three sources k=1,2,3 are solutions of a linear Fokker-Planck equation The rapidity is , the equilibrium value [3] of the rapidity yeq, the rapidity diffusion coefficient Dy, and the relaxation time  y . For unidentified charged hadrons, the distribution functions are converted to pseudorapidity space. The total distribution function is an incoherent sum of the solutions Rk with the appropriate particles numbers in the three sources. Within this analytical framework, I discuss the gradual approach of the many-body system to local thermal equilibrium for symmetric (Au+Au) and asymmetric (d+Au) cases, and obtain precise agreement with the experimental BRAHMS and PHOBOS results. Longitudinal collective expansion velocities are determined. The transport coefficients are then extrapolated from Au + Au at RHIC energies ( sNN =19.6 200 GeV) to Pb + Pb at LHC energies sNN = 5.52 TeV. Rapidity distributions for net protons, and pseudorapidity spectra for produced charged particles [4] are obtained and discussed in the three-sources RDM at LHC energies. References: [1] G. Wolschin, Eur. Phys. J. A5 (1999) 85; Europhys. Lett. 47 (1999) 30; Phys. Lett. B 569 (2003) 67; Europhys. Lett. 74 (2006) 29. [2] M. Biyajima, M. Ide, M. Kaneyama, T. Mizoguchi, and N. Suzuki, Prog. Theor. Phys. Suppl. 153 (2004) 344. [3] G. Wolschin, M. Biyajima, T. Mizoguchi, and N. Suzuki,Phys. Lett. B 633 (2006) 38; Annalen Phys. 15 (2006) 369. [4] R. Kuiper and G. Wolschin, in preparation. 271. QUARK-QUARK DOUBLE SCATTERING IN NUCLEI WITH TWIST-EXPANSION APPROACH Ben-Wei Zhanga,b, Xin-Nian Wangc and Andreas Sch¨aferd of Particle Physics, Central China Normal University, Wuhan, 430079, P. R. China, [email protected] bCyclotron Institute and Physics Department, Texas A&M University College Station, Texas 77843-3366, USA cNuclear Science Division, MS 70R0319, Lawrence Berkeley National Laboratory Berkeley, CA 94720 USA, [email protected] dInstitut fu¨r Theoretische Physik, Universita¨t Regensburg, D-93040 Regensburg, Germany, [email protected] aInstitute Multiple scattering in a nuclear medium has been used as an excellent tool to study properties of both hot and cold nuclear matter. In this work we investigate the properties of quark-quark double scattering in eA DIS and its contribution to quark and anti-quark fragmentation functions with the generalized factorization theorem of twist-4 processes in perturbative QCD. It is shown that quark-quark double scattering may mix quark and gluon fragmentation functions and provide a mechanism to change the jet flavor in medium. In addition, we find that quark-quark double scattering will give different corrections to quark and anti-quark FF and the modification to anti-quark fragmentation function is larger that the modification to quark fragmentation function. This difference may cast light on the remarkable observation by the HERMES Collaboration [1,2] that whereas the multiplicity ratios for positive and negative pions are similar, a larger difference is 133 observed between protons and antiprotons produced by parton fragmentation. References: [1] A. Airapetian et al. [HERMES Collaboration], Eur. Phys. J. C 20, 479 (2001). [2] A. Airapetian et al. [HERMES Collaboration], Phys. Lett. B 577, 37 (2003). 272. DECIPHERING THE PROPERTIES OF THE MEDIUM PRODUCED IN HEAVY ION COLLISIONS AT RHIC BY A pQCD ANALYSIS OF QUENCHED LARGE p⊥ PION SPECTRA R. Baiera and D. Schiffb Physics Department, University of Bielefeld, D-33501 Bielefeld, Germany, [email protected] b LPT, Bat. 210, Universit´e Paris-Sud,F-91405 Orsay, France, [email protected] a We discuss the question of the relevance of perturbative QCD calculations for analyzing the properties of the dense medium produced in heavy ion collisions.Up to now leading order perturbative estimates have been worked out and confronted with data for quenched large p⊥ hadron spectra. Some of them are giving paradoxical, even contradicting results and are leading to speculations such as the formation of a strongly interacting quark-gluon plasma. Trying to bypass some drawbacks of the leading order analysis and without performing detailed numerical investigations we collect evidence in favour of a consistent description of quenching and of the characteristics of the produced medium within the pQCD framework. Full presentation in: arXiv hep-ph/ 0605183 v2 273. QUARKONIA CORRELATORS AND SPECTRAL FUNCTIONS A. Jakov´aca,P. Petreczkyb, K. Petrovc and A. Velytskyd of Physics, BME, Budapest, 1111, Hungary, [email protected] bDepartment of Physics and RIKEN-BNL Brookhaven National Laboratory, Upton, NY, 11973, USA, [email protected] c The Niels Bohr Institute, Copenhagen, 2100, Denmark, [email protected] bDepartment of Physics and Astronomy University of California at Los Angeles, Los Angeles 90095, USA, [email protected] aInstitute We are going to present lattice calculations of quarkonium correlators and spectral functions performed on quenched anisotropic lattice with lattice spacings at-1 = 14.12, 10.89, 8.18, 4.11GeV, ξ = as/at = 2, 4.We extract the spectral function using the Maximum Entropy Method (MEM). At zero temperature we can identify the ground state and separate the excited states from the continuum. Having several lattice spacings allows us to show that the effects of finite lattice spacing show up in the spectral function only at energies ω > 5GeV . The analysis of the charmonia correlators and spectral functions shows that 1S charmonia survive till temperatures as high as 1.5Tc while the 1P states are dissolved at temperatures T = 1.1 − 1.2Tc. We examine the robustness of this statement for different lattice spacings and choices of the priors which go into MEM. We find indications that 1S charmonia states dissolve at temperatures T ∼ 2Tc. Collective effects in the plasma show up as structures in the spectral functions at small ω < T . We discuss the difficulties in identifying the transport contribution to the vector spectral function. We also study charmonia correlators spectral functions at finite momentum p and show that their behavior indicates the presence of the contribution below the light-cone, ω < p (Landau damping). Calculation of the bottomonia correlators and spectral functions indicate that 1S bottomonia states may survive till temperatures as high as 3Tc. At the the time we find strong modification of the 1P bottomonia states already at T = 1.1 − 1.2Tc. Please send all correspondence to P´eter Petreczky, Bldg. 510a, Brookhaven National Laboratory, Upton NY 11973, [email protected] . References: [1] A. Jakov\'ac, PP. Petreczky, K. Petrov, A. Velytsky, hep-lat/0603005 and paper in progress [2] P. Petreczky, hep-lat/0606007 134 274. PION NUCLEON INTERACTION IN A LINEAR SIGMA MODEL WITH HIDDEN GAUGE SYMMETRY S. Wilmsa and D. H. Rischkea Institute for Theoretical Physics, Johann Wolfgang Goethe-University Frankfurt, Hessen, 60438, Germany, [email protected] a We investigate the linear sigma model with U(2)L  U(2)R symmetry. The Lagrangian of this model contains scalar and pseudoscalar mesons. We add vector and axial vector mesons as well as chiral nucleons following the principle of local non-abelian gauge invariance. Chiral symmetry breaking introduces bilinear terms coupling the a1 to the pion as well as the f1 to the eta meson. These terms have to be eliminated by a shift of the axial vector meson fields. This shift generates a p-wave pion-nucleon interaction. In a first step, we investigate pion-nucleon scattering at tree level. Further work focusses on the modifications of hadronic spectral properties in a hot and dense medium. 275. ANOMALOUS VISCOSITY OF AN EXPANDING QUARK-GLUON PLASMA M. Asakawaa1, B. Mu¨llerb, and S.A. Bassc of Physics, Osaka University,Toyonaka, Osaka 560-0043, Japan, [email protected] bDepartment of Physics, Duke University, Durham, NC 27708, U.S.A., [email protected] cDepartment of Physics, Duke University, Durham, NC 27708, U.S.A., [email protected] aDepartment We argue that an expanding quark-gluon plasma has an anomalous viscosity, which arises from interactions with color fields dynamically generated by the Weibel instability. We derive an expression for the anomalous viscosity in the turbulent plasma domain and apply it to the hydrodynamic expansion phase, when the quark-gluon plasma is near equilibrium. The anomalous viscosity dominates over the collisional viscosity for weak coupling. This effect may provide an explanation for the apparent nearly perfect liquidity of the matter produced in nuclear collisions at RHIC without the assumption that it is a strongly coupled state and that the collisional viscosity dominates the total viscosity. References: [1] M. Asakawa, B. Mu¨ller, and S.A. Bass, Phys. Rev. Lett. 96 (2006) 252301 (preprint hep-ph/0603092). 276. FORGOTTEN NUCLEAR EFFECTS IN HIGH-ENERGY HEAVY-ION COLLISIONS a b A. Szczurek a b Institute of Nuclear Physics PL-31-342 Cracow, Poland,[email protected] University of Rzesz´ow PL-35-959 Rzeszow, Poland We present three different simple nuclear physics effects which were either totally ignored or their role was not discussed so far in the literature. It has been argued recently that the so-called nuclear modification factor (RAA) is an observable useful for identifying the quark-gluon plasma. We discuss the effect of Fermi motion in nuclei on RAA at CERN SPS and BNL RHIC energies. Contrary to the simple intuition, rather large effects are found for CERN SPS. The Fermi motion in nuclei contributes sig- nificantly to the Cronin effect. The effect found is qualitatively similar to the one observed experimentally at CERN energies and similar to the one obtained in the models of multiple scattering of initial partons. We predict different size of the effect for different types of hadrons, especially at low energies. The theoretical nuclear physics predictions and experimental results on antiprotonic atoms lead to different proton and neutron spatial distributions. At CERN SPS energies production of positive and negative pions differs for pp, pn, np and nn scattering. These two facts lead to an impact parameter dependence of the π+ to π− ratio in 208P b +208 P b collisions. A recent experiment at CERN seems to confirm qualitatively these predictions. The results for two models considered are almost identical. It may open a new possibility for determination of neutron density distribution in 135 nuclei. The charged pions (kaons) produced in peripheral heavy-ion collisions are subjected to strong electromagnetic fields of charged spectators - remains of the nuclear collision. The ratio of π+/π− in Pb-Pb collisions is calculated as a function of the Feynman xF , pion transverse momentum and impact parameter at SPS energies including electromagnetic distortion effect due to the charge of the moving spectators. A deep hole in the ratio is predicted at xF ∼0.15 and small transverse momenta for peripheral collisions, fairly independent of the beam energy. We predict analogous effect for the K +/K − ratio concentrated at somewhat larger xF. The electomagnetic effect considered can be a handle for a better understanding of the particle formation process. The presentation is partially based on [1],[2],[3]. References: [1] A. Szczurek and A. Budzanowski,“Fermi motion and nuclear modification factor”, Mod. Phys. Lett. A19 (2004) 1669. [2] P. Pawlowski and A. Szczurek, “Neutron spatial distribution in nuclei and the impact-parameter dependence of the π+ − π−asymmetry in heavy-ion collisions”, Phys. Rev. C70 (2004) 044908. [3] A. Rybicki and A. Szczurek, a paper in preparation for Phys. Rev. C. 277. Spectrum of soft mode with thermal mass of quarks above critical temperature Y. Hidakaa and M. Kitazawaa BNL Research Center, Brookhaven National Laboratory Upton, New York 11973, U.S.A., [email protected] aRIKEN We study effects of thermal mass of quarks, mT , on the spectrum of mesonic excitations in the scalar and pseudo-scalar channels above the critical temperature TC of the chiral phase transition [1]. It is known that the quarks have thermal mass which does not broken the chiral symmetry and is different from the Dirac mass. Such a thermal mass can be calculated using the hard thermal loop (HTL) approximation at extremely high temperature [2]: In the HTL approximation the quark spectrum consists of the standard quasi- particle mode, plasmino excitation mode and continuum which corresponds to the Landau damping process. Our aim of this work is to explore how such quark spectra affect the mesonic excitations near TC if they survive. It is known that there arise the soft modes in the scalar and pseudo-scalar channel with a large strength due to the chiral order parameter having large fluctuations above TC if the phase transition is second or weakly first order [3]. We show the soft modes appear due to the chiral symmetry even though quarks have thermal mass. One of important effects of thermal mass is decays of the soft modes into quasi states. They are suppressed if the soft modes are lighter than twice of quasi particles 2m T and thus one may say that the soft mode is expected to become stable. However, we show the soft mode has large decay rate even below 2mT due to contribution of continuum. We note that the quarks have the Landau damping process when quarks have thermal mass. A characteristic feature of our result is that two peaks are seen at low energy region of the spectrum due to Van Hove singularities, which are related to scattering between the soft mode and plasmino. In the more realistic quark spectrum, the two peaks at low energy may become obscure owing to the width of collective modes. However, the remnant of two peaks would be seen as a dip of the spectrum even such a case. References: [1] Y. Hidaka and M. Kitazawa, in preparation. [2] M. Le Bellac, Thermal Field Theory (Cambridge University Press, Cambridge England 1996). [3] T. Hatsuda and T. Kunihiro, Phys. Rev. Lett. 55, 158 (1985); C. DeTar, Phys. Rev. D 32, 276(1985). 278. Shear viscosity in weakly coupled N =4 Super Yang-Mills S. Jeona,b, S. Huota, and G. D. Moorea of Physics, McGill University,Montreal, Quebec, H3A-2T8, CANADA, [email protected] bThe presenting author. aDepartment We compute the shear viscosity of weakly coupled N=4 supersymmetric Yang-Mills (SYM) 136 theory. Our result for η/s, the viscosity to entropy-density ratio, is many times smaller than the corresponding weak-coupling result in QCD. This suggests that η/s of QCD near the transition point is several times larger than the viscosity bound, η/s > 1/4π. References: [1] hep-ph/0608062, Shear viscosity in weakly coupled Simon C. Huot, Sangyong Jeon, Guy D. Moore =4 Super Yang-Mills theory com- pared to QCD, by X. Future Experiments and Facilities 279. Trigger Decision Criterion of the ALICE Photon Spectrometer Yaping Wang a and Xu Cai b Institute of Particle Physics, Central China(Huazhong) Normal University Wuhan, Hubei, 430079, P. R. China, [email protected] b Institute of Particle Physics, Central China(Huazhong) Normal University Wuhan, Hubei, 430079, P. R. China, [email protected] a The ALICE PHOton Spectrometer(PHOS) is electromagnetic calorimeter, consists of 5 identical modules, each containing a matrix of 56*64 PWO4 crystals. Each module covers 20 degree of azimuthal angle, mapping exactly with the TPC sectors. The role of PHOS in ALICE experiment is to detect and identify real photons and measure their 4-momentum exploiting direct photons and light neutral mesons(pion and η mesons mainly). The unique ability of PHOS to measure identified particles over a broad dynamical range in transverse momentum will enable to access key information on the soft and hard processes occurring in pp and AA collisions at LHC energy. PHOS trigger decision system provides level-0(L0) and level-1(L1) trigger for ALICE trigger system. The PHOS L0 trigger is conceived as a minimum bias trigger for high luminosity p−p interactions at a latency of 800 ns, and the L1 trigger is sensitive to high pT photons in Pb−Pb interactions at a maximum latency of 6.2 us. Before the ALICE running, but the running criterion and parameters selection for PHOS trigger decision system should be determined primarily. This talk will study trigger decision criterion of the PHOS in the ALICE experiment by Monte Carlo simulations, including four parts: 1) an overview of trigger decision criterion of PHOS; 2) the energy reconstruction performance of PHOS; 3) the selection of trigger threshold and the event trigger efficiency distribution; 4) the event trigger rate of PHOS and its selection in p−p and Pb−Pb collision mode. References: [1] Hans Specht, Nucl. Phys, v. A698, p. 341-359, 2002. [2] Cai Xu, and Zhou Dai-Mei, HEP and NP, v. 26(9), p. 971-990, 2002. [3] ALICE Collaboration, ALICE Technical Proposal , CERN/LHCC/95-71. [4] ALICE Collaboration, ALICE TDR of the PHOS, CERN/LHCC/1999-04. [5] CERN Program Library, Geant Detector Description Tool , V3.21, W5103 CERN, 1994. [6] ALICE Collaboration, http://aliweb.cern.ch/offline. [7] ALICE Collaboration, ALICE PPR, V. II, CERN/LHCC/2005-0NN. [8] Hans Muller, et al, NIM A, v. 518, p. 525-528, 2004. [9] ALICE Collaboration, ALICE PPR, V. I, CERN/LHCC/2003-049. [10] Loizides. A, http://xxx.lanl.gov/nucl-ex/0501017 , v. 1. [11] Moraes. M, Minimum bias interactions and the underlying event, ATLAS-UK Physics Meeting, 2002. 280. The Laser of the ALICE's Time Projection Chamber G. Renault a, B.S. Nielsen a, J. Westergaard a and J.J. GaardhΦ je a for the ALICE Collaboration a Niels Bohr Institute, Blegdamsvej 17, Copenhagen, 2100, Denmark, [email protected] The large (88 M3) TPC of the ALICE detector at CERN has in the early summer measured the first tracks from injected laser rays and from cosmic rays. A wide laser beam is split into several hundred narrow beams by fixed micro-mirrors at stable and known positions throughout the TPC. 137 These narrow beams generate straight tracks in the drift volume by two photon ionization at many angles. Other electrons were emitted by photoelectric effect when the laser beam hits metallic surfaces such as the central electrode, the mylar strips of the electric field cage, wires and pads of the readout system. In this talk the basic principles of operation of the 266 nm laser will be presented, showing the installation and adjustment of the optical system and describing the detector control system. The collection of the first tracks and comparisons to simulations will be discuss. 281. The CBM experiment at FAIR - planning for an investigation of the intermediate range of the QCD phase diagram – a C. Höhne a for the CBM collaboration GSI, Planckstr. 1, 64291 Darmstadt, Germany， [email protected] The Compressed Baryonic Matter (CBM) experiment at the future Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt will be a dedicated heavy-ion experiment exploring the QCD phase diagram in the region of moderate temperatures but very high baryon densities. This region of the phase diagram attracted strong attention in recent years as here several highly interesting features of QCD can be addressed experimentally: The phase boundary between hadronic and partonic matter is expected to be of first order in this range running into a critical endpoint before becoming a crossover at the top-SPS and RHIC energies. An experimental determination of either any point on the first order phase boundary or even the critical point would be a milestone in our understanding of the QCD phase diagram. This region is furthermore characterized by the enormously high baryon densities created in the heavy-ion collisions which have not been studied in detail so far. Addressed subjects will be the chiral symmetry restoration and the nuclear equation of state at high densities. CBM, as a 2nd generation experiment for this region of the phase diagram, will face these questions investigating observables not been studied before in this range: charm, dileptons, fluctuations, correlations and flow of identified particles. All these aspects of hadron production will be measured from p+p to A+A for beam energies from 15 to 35 AGeV for Au+Au collisions and up to 45 AGeV for A/Z=0.5 nuclei. This ambitious experimental program will require high beam intensities resulting in high reaction rates posing the main challenge for design and development of the CBM detector. The main components of this fixed target experiment will be a high resolution Silicon Tracking System in a magnetic dipole field, time-of-flight detectors for the identification of hadrons, and an electromagnetic calorimeter. Dileptons will either be measured in the electron channel using a Ring Imaging Cherenkov Counter and Transition Radiation Detectors or in the muon channel with an active muon-absorber system. In this talk the status of the CBM experiment will be given, in particular concerning feasibility studies of its key observables as charm production and dileptons. Detector development issues will be covered as well. 282. PERFORMANCE OF FORWARD RESISTIVE PLATE CHAMBERS FOR MUON TRIGGERING AT CMS/LHC S. H. Ahn, B. Hong, M. Ito, T. I. Kang, B. I. Kim, H. C. Kim J. H. Kim, K. B. Lee, K. S. Lee, S. Park, M. S. Ryu, K. S. Sim on behalf of the CMS Forward RPC Collaboration Korea Detector Laboratory, Korea Univeristy, Seoul, 136-701, Republic of Korea, [email protected] The Compact Muon Solenoid (CMS), which is one of three major detector systems at LHC, is primarily optimized for muon detection, as represented by its name [1]. Although the CMS is primarily to study proton-proton collisions at 14 TeV, it also plans to study heavy-ion collisions at 5.5 TeV per NN collision in the center-of-mass. Not only for proton-proton collisions, but also for heavy-ion collisions, muon detection is the most natural and powerful tool to isolate interesting signals and events over significant backgrounds, as a spotlighted signal of quark-gluon plasma is the production of heavy vector mesons (J/ψ and γ families) and their decays into two muons [2]. From the experiences at the SPS and RHIC experiments, the best mass resolution of heavy vector 138 mesons can be achieved with two muons because muons are less affected than electrons by radiative losses in the detector materials. In this paper, we will present the development and the construction of the forward resistive plate chambers for the CMS. The standard double-gap geometry, which was designed and constructed by the Korea Detector Laboratory, satisfies all aspects of the CMS requirements, including the muon detection efficiency, the time resolution, the working high-voltage plateau range, the noise cluster rate, and the power consumption. These results clearly demonstrate that the present design of the RPC is suitable for the muon trigger system in the endcap region of the CMS detector.The production and the quality assurance procedures for the mass production will be also presented. The percentage to produce the qualified gas gaps is now reach above 80 %. We also report an intensive aging study of the forward RPCs performed by using a 200 mCi 137 Cs gamma-ray source. A few diagnostic methods to observe aging phenomena are discussed. The test result is equivalent to approximately 12 years of the CMS operation. Future perspectives of the forward RPCs related to the CMS heavy-ion program is presented. References: [1] CMS, The Muon Project, Technical Design Report, CERN/LHCC 97-32, 15 Dec. 1997. [2] F.~Karsch, D.~Kharzeev, and H. Satz, Physics Letters B, v.637, p.75-80, 2006. [3] S. Parket al., Nuclear Instruments and Methods in Physics Research A, v.550, p.551-558, 2005. [4] B. Hong et al., Nuclear Instruments and Methods in Physics Research A, v.533, p.32-36, 2004. 283. The Time of Flight detector of the ALICE experiment E. Scapparone on behalf of the ALICE-TOF group INFN-Bologna, Bologna, 40126, Italy, [email protected] The particle identification (PID) power of a large time of flight system, covering the central region, is of crucial importance in the high-energy heavy-ion experiments. The goal of the ALICE Time of Flight detector (TOF) is to perform pion/kaon/proton separation at |η|<1 in the intermediate momentum range (up to a few GeV/c). The TOF barrel, based on the Multigap Resistive Plate Chamber (MRPC) detector, has an area of ≈160m2. The TOF is arranged in 18 Supermodules, each instrumented with 91 MRPC strips. The MRPC strip consists of two stacks of resistive plates, spaced one from the other with equal sized spacers, creating a series of uniform gas gaps, with voltage applied to the external surfaces. Electrodes are connected to the outer surfaces of the stack of resistive plates while all the internal plates are left electrically floating. The MRPC stack is made of 6 glasses, forming 5 gaps. Each gap has a width of 250 μm and is filled with a gas mixture C2F4H2(90%)/SF6(5%)/C4H10(5%). The high segmentation (~160,000 readout pads, 2.5 × 3.5cm2 each) allows to keep the occupancy below 15% in Pb-Pb interaction taking place at LHC at s = 5.5 TeV per nucleon pair. A dedicated ASIC is the key component of the fast, low consumption front-end electronics. Each Supermodule is read out by four VME crates, each containing High-Performance TDC (HPTDC), reading the MRPC-pad time information. Taking advantage of several years of R&D, the MRPC prototypes reached an intrinsic time resolution smaller than 50 ps and an efficiency of 99.9%. In this paper we present the physics goals of the TOF, the basic concepts of the MRPC detector, the R&D result, the Supermodules assembly procedure and mounting status. 284. The ALICE Forward Multiplicity Detector and Readout Christian Holm Christensen a and Kristján Gulbrandsen a Niels Bohr Institute, University of Copenhagen Blegdamsvej 17, 2100 Copenhagen \O, Denmark [email protected] and [email protected] The ALICE experiment is designed to study the properties of hadron and nucleus collisions in a new energy regime at the Large Hadron Collider at CERN. A fundamental observable in such collisions is the multiplicity distribution of charged particles. A forward multiplicity detector (FMD) 139 has been designed to extend the charged particle multiplicity coverage of the ALICE experiment to rapidities of -3.4<η<-1.7 and 1.7<η<~5.0. Furthermore, the FMD can, with its relatively high azimuthal segmentation, provide independent event-plane and azimuthal flow measurements at forward rapidities. The FMD consists of five rings of silicon strip detectors with 10240 Si strips per ring. Each ring is divided into sectors comprised of silicon sensors bonded and glued to hybrid PC boards equipped with radiation hard preamplifier chips, individually receiving the signals from 128 Si strips. These signals are multiplexed to digitization boards located directly behind the hybrid PC boards on the detector frame. An off-the-shelf FPGA located on each digitization board directs the readout sequence from the preamplifier chips and, furthermore, provides a mechanism to control the preamplifiers' behaviour and monitor crucial voltages and currents. Custom-made fast ADC chips located on the digitization boards digitize all the signals from up to 16 preamplifier chips. A separate read out controller pushes the data from multiple ADC chips over optical fibers, for maximum throughput and low noise, to a data acquisition farm and has the additional capability to configure the ADC chips and digitization board. The data acquisition farm consists of commodity Linux machines with special memory segmentation for data handling. The design, characteristics, and performance of the ALICE forward multiplicity detector and readout will be discussed. 285. Proton-proton physics with the ALICE muon spectrometer at the LHC N. Bastid for the ALICE Collaboration LPC Clermont-Ferrand, IN2P3-CNRS and Université Blaise Pascal, 63177 Aubière Cedex, France, [email protected] ALICE, the dedicated heavy ion experiment at LHC, will investigate strongly interacting matter at extreme energy densities, formed in Pb-Pb collisions. The successful achievement of the heavy ion program requires also the study of proton-proton, proton-nucleus, and light nucleus-nucleus systems. Proton-proton collisions are of great interest since besides providing the necessary baseline for nucleus-nucleus collisions, they allow to test both perturbative and non-perturbative regimes of QCD in a new phase space region associated with large Q2 and very low Bjorken x values. Moreover the ALICE proton-proton physics program complements the one of the dedicated proton-proton experiments at the LHC. A particular emphasis will be placed on the physics analyses foreseen with the ALICE muon spectrometer, with first proton-proton beams delivered by the LHC. 286. Probing partonic distribution functions in nucleons and nucleus with Forward Calorimeters in the PHENIX experiment at RHIC aDepartment E. Kistenev a for the PHENIX Forward Upgrade Collaboration of Physics, Brookhaven National Laboratory,Upton, NY, 11933, USA, [email protected] The physics goals and major components of the PHENIX Forward Calorimetry Upgrade are presented. The new subsystem is designed to increase acceptance for the forward produced electromagnetic probes in pp, pA and AA collisions in the PHENIX experiment ten-fold. The upgrade will serve to maintain and expand PHENIX leading role in the direct photon production studies. Measurements of the correlated photon-jet production will be critical to the studies of the spin dependent structure functions. Photonic decays of the charmonium states such as the χc to J/ψ +γ hold keys to understanding charmonium suppression in heavy ion Collisions, forward production of inclusive jets, direct photons or Drell-Yan pairs at large xF in nucleon-ion collisions at RHIC will provide a new window for the observation of saturation phenomena expected at high parton number densities. The Forward Calorimetry Subsystems (North and South) will both consist of Tungsten-Silicon Nose Cone tracking calorimeters with rapidity coverage 0.9< η <3 and Crystal (PbWO4) Muon Piston Calorimeters occupying existing recesses inside muon spectrometer iron return yokes and 140 covering the range of 3.2 <η< 4. The South MPC was installed into PHENIX last year and was already accumulating data during Run6 PHENIX data taking period. The North MPC will be installed shortly. Funding commitments to NCC construction are pending. This talk will summarize basic design ideas of the PHENIX Forward Calorimeters, briefly present available performance data collected in the test beam and during PHENIX running and will use simulation to prove that highly segmented tracking calorimeters could be used to separate overlapping photons from high momentum π0 decays down to the γ-γ separation distances ~RMoliere/4 and to measure the direct photon yield. 287. Progress of ALICE-PHOS Detector at LHC ZHOU Daicui For the ALICE-PHOS collaboration Institute of Particle Physics, Central China Normal University,Wuhan, 430079, P. R. China, [email protected] The physics of photons from heavy-ion collisions at the LHC energy will be discussed, in particular, in the light of the RHIC results. The high-resolution photon spectrometer (PHOS) of the ALICE experiment based on the lead tungstate crystals will be described. Results of beam tests will be discussed in comparison with simulation results. The further development of the PHOS spectrometer will be presented, including construction of the first (out of five) PHOS module, and results of its commissioning and calibration with the electron beam. References: [1] N.Ahmad et al., ALICE Collaboration, ALICE Physics Performance Report Vol. II, CERN/LHCC 2005-030, (Dec.2005). To be published on Phys. Jan. G. [2] N. Ahmad et.al, ALICE Collaboration, ALICE Physics Performance, Report Vol. I, J.Phys. G: Nucl. Part.Phys,30(2004)1517-1763 D.Schiff Nucl. Phys. B483(1997)291 [3] N. Ahmad et. al., ALICE Collaboration, ALICE technical Proposal: Photon Spectrometer, CERN/LHCC99-4, ALICE TRD2 (1999). [4] N. Ahmad et al., ALICE Collaboration, ALICE technical Proposal, CERN/LHC 95-71,LHCC/P3,(1995)[6]988)607 288. PROBABILISTIC HEAVY ION JET RECONSTRUCTION FOR RHIC AND LHC Y. S. Laia of Physics, Columbia University, 538 West 120th Street New York, NY, 10027-6601, USA, [email protected] aDepartment Currently, hard scattering processes in heavy ion collisions are studied via single high-pT hadron production and di- or tri-hadron correlations. Both at RHIC and in intermediate pT < 50 GeV/c at the LHC, the high multiplicity soft background of heavy ion collisions prevents the use of traditional jet reconstruction algorithms ([1, 2]). Hard probes at inter-mediate energies could provide an especially rich insight into the properties of the dense matter, and a full jet reconstruction would provide more information about jet energy loss and/or in-medium jet fragmentation than the highly limited particle correlation observables. But studying these intermediate energy hard probes using jet reconstruction requires an in- algorithm robustness against the soft background and the ability to separate jet fragments from the background. Such a separation is not provided by e.g. the traditional kT algorithm. We describe a new algorithm being studied for jet reconstruction in heavy ion collisions at both RHIC and LHC that attempts to use a likelihood analysis to statistically separate the fragments of energetic jets from the soft background. Within this framework, it is even possible to ccommodate structures in the soft background such as fluctuations and finite v2, that otherwise would seriously distort the jet reconstruction. We further provide its effcient implementation with an O(N2) complexity, which is also optimal with respect to the worst-case complexity limit for a probabilistic jet reconstruction. This new algorithm exhibits a low complexity feature similar to the effcient implementations of the kT algorithm [3]. References [1] J. E. Huth et al., in Research Directions For The Decade, Proceedings of the Summer Study, Snowmass, 141 Colorado, 1990, edited by E. L. Berger (World Scientific, Singapore, 1992), p. 134. [2] S. D. Ellis and D. E. Soper, Phys. Rev. D 48, 3160 (1993). [3] M. Cacciari and G. P. Salam, Laboratoire de Physique Thèorique et Hautes Energies Report LPTHE-05-32, 2005 (arXiv:hep-ph/0512210). 289. Low-x QCD with CMS at CERN-LHC David d’Enterria for the CMS Collaboration CERN, Geneva, Switzerland, E-mail [email protected] The LHC will provide proton-proton, proton-nucleus and nucleus-nucleus collisions at s NN =14, 8.8, 5.5 TeV respectively. The range of fractional momenta of the colliding partons will be x  2 pT ≈ 70–30 times lower than equivalent collisions at RHIC (i.e. of the order x s NN ~10−3 for typical hard probes at midrapidity). At forward rapidities, the relevant Bjorken x values can be as low as x ∝ e−y~10−6 . In such low-x regime, non-linear gluon-gluon processes, - as described in the Color-Glass-Condensate picture -, will likely dominate the parton structure and evolution of the wave function of the colliding hadrons. The Compact Muon Solenoid (CMS) experiment at CERN LHC has unparalleled capabilities for the measurement of particles in the forward hemisphere. The combination of the forward hadronic calorimeter HF (3< |η| <5), the CASTOR sampling calorimeter plus Totem T2 tracker (5.5< |η| <6.6), and the zero-degree calorimeter ZDC (|η| >8.1 for neutrals), makes of CMS an almost complete 4π detector, very well adapted to study the physics of gluon saturation and non-linear parton evolution at small fractional momentum x. The unique physics potential of low-x QCD studies at CMS will be presented and several perturbative channels in p+p, p+A and A+A collisions at LHC energies such as (i) quarkonia photoproduction in ultraperipheral A+A, (ii) Drell-Yan measurements in CASTOR, and (iii) forward jet measurements in HF, will be discussed. 290. Electronics performance of the calorimeter PHOS Z. Yin a and H. Műller b of Particle Physics, Huazhong Normal University Wuhan, 430079, P. R. China, [email protected] bCERN, PH department, 1211 Geneva 23 , Switzerland, [email protected] aInstitute 3%  0.8% , for a pT range of 100 E MeV/c - 100 GeV/c, new PHOS electronics has successfully passed a test beam within the first module consisting of 56 x 64 PbWO4 crystals and 3584 APDs. The beam test data, taken with 2 GeV/c electrons, confirms the above goal with a noise term of < 7 MeV for a matrix of 3×3 at an ambient temperature of -24°C and achieves a derived timing resolution of < 2ns for TOF cuts. Due to precision bias control hardware for the APD's, built into the electronics, the inter-calibration level for the constant term could be better than the initial requirement. The linearity of the 14 bit dynamic range was tested with a tuneable LED source to < 1%. Whilst our results confirm this electronics choice as baseline for both the PHOS and EMCal detectors of ALICE, an upgrade towards a higher dynamic range with standard, optical readout is planned, also in perspective of new applications with Silicon Photomultipliers. Following the requirement of an energy resolution of 291. RELATIVISTIC HEAVY ION COLLIDER (RHIC) ACCELERATOR FACILITY: PRESENT AND FUTURE* D.I. Lowenstein Collider-Accelerator Department, Brookhaven National Laboratory Upton, NY 11973-5000 USA, [email protected] 142 The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory operates two unique physics programs. RHIC is both a heavy ion and a polarized proton collider that focuses on the study of QCD. The facility supports a user community of over 1200 physicists from 18 nations. Since its first operation in 2000, RHIC’s unique heavy ion program has discovered a new form of quark-gluon matter and is presently probing its properties. The polarized proton program is investigating the spin structure of the proton at center-of-mass energies up to 500 GeV. The evolution of the accelerator facility consists of a new preinjector system based on an EBIS source, a RFQ and an IH linac, which will be commissioned in 2009; a ten-fold ion luminosity enhancement (RHICII) using both stochastic and electron cooling based on an energy-recovery-linac, which is planned for a construction start in 2009; and the addition of an electron capability (eRHIC) to provide both electron-ion and polarized electron-polarized proton collisions. A status of the EBIS Project, the cooling research and development efforts, and the eRHIC design will be presented. *Work performed under the auspices of the U.S. Department of Energy. 292. High Level Trigger applications for the ALICE experiment M. Richter a, T. Alt b, S. Bablok a, C. Cheshkov c, P. T. Hille d, V. Lindenstruth b, G. Ǿvrebekk a, D. R•ohrich a, B. Skåli d, T. M. Steinbeck b, J. Thäder b, K. Ullaland a, for the ALICE collaboration a Department of Physics and Technology, University of Bergen Allegaten 55, 5007 Bergen, Norway, [email protected] b Kirchho_ Institute of Physics, University of Heidelberg Im Neuenheimer Feld 227, 69120 Heidelberg, Germany c CERN, European Organization for Nuclear Research, Geneva,CERN, 1211 Geneva 23, Switzerland d Department of Physics, University of Oslo, Postboks 1048 Blindern, 1316 Oslo, Norway The ALICE experiment at the LHC is designed to run at an event rate up to 200 Hz for central Pb-Pb collisions. The expected data rate is about to 25 GByte/sec while the limit of the Data Acquisition system (DAQ) is at 1.2 GByte/sec. In order to reduce the data rate, a High Level Trigger system (HLT) was designed which allows on-line data processing at the full input rate and e_cient data rate reduction. To accomplish this task, a computing cluster of several hundred dual-processor nodes is being installed. Fast on-line reconstruction of the event is the first step. Specific processing components carry out tasks like local pattern recognition, tracking, hough tracking and event merging, and are arranged in an hierarchical analysis chain. Based on the analysis of the reconstructed event, trigger decisions are calculated and are transmitted to the DAQ system. Data reduction is mainly achieved by partial detector read-out, intelligent event selection, and data compression algorithms. Further HLT applications include short event summary data (ESD), on-line detector monitoring, and calculation of calibration data. A common interface for HLT processing components has been designed to run the components from either the on-line or offline analysis framework without changes. The interface adapts the component to the needs of the on-line processing and allows the developer at the same time to use the offline framework for easy development, debugging, and benchmarking. Results can be compared directly. A major system integration test was carried out during the commissioning of the Time Projection Chamber (TPC) and the Photon Spectrometer (PHOS), where HLT is part of the monitoring system. The HLT processing capability is indispensable for the PHOS detector, where the on-line pulse shape analysis reduces the data volume by a factor 20. The talk describes briey the architecture of the HLT system. It focuses on typical applications and component development. Benchmarks and first results from the TPC/PHOS commissioning will be presented. 293. Detector Construction Database for ALICE Experiment 143 Wiktor S. Peryt for ALICE Collaboration Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warsaw, Poland ALICE1 collaboration, which prepares one of the biggest physics experiments in the history, is in the production phase of its detector components. The experiment will start at LHC2 at CERN in 2007/2008. In the meantime about 1000 people from ~70 institutions are involved in this enterprise. ALICE detector consists of many sub-detectors, designed and manufactured in many laboratories and commercial firms, located mainly in Europe, but also in the U.S. and India To assure appropriate working environment for such a specific task, strictly related to tests of particular components, measurements and assembly procedures a Detector Construction Database system (DCDB) has been designed and implemented at CERN and some labs involved in these activities. The group of young computer scientists (mainly PhD and undergraduate students) from the Warsaw University of Technology, lead by the author, has designed and developed the system for the whole experiment. New, quite innovative approach to the complex detector construction database system design is presented in the paper. The most specific features of applied mode are the following: (i) distributed (local) databases located at laboratories involved in production, test and assembly of components and central repository located at CERN, (ii) generic data structures used in design of both central and local databases. (iii) advanced monitoring system with check-in/check-out capabilities for components' flow between labs (iv) making use of generic data structures in user application, common for quite different sub-detectors. (v) using of XML language for data transfers between local databases and the central one. Management of information about cables, racks, crates and electronics modules is also included in this system, being its essential advantage. DCDB system has been developed in the frame of ALICE off-line project but it is generic and universal enough to serve also other similar enterprises. Keywords: heavy ions, LHC, quark-gluon plasma, database, IT software technologies, ALICE experiment 294. Quarkonia Detection in the ALICE Experiment G. Martínez Garcíaa for the ALICE Collaboration Subatech (CNRS/IN2P3 - Ecole des Mines de Nantes - Unversité de Nantes BP 20722, 44307 Nantes cedex, France, [email protected] a Quarkonia production is a unique probe to study Quark Gluon Plasma formed in nucleus-nucleus collisions at LHC energies. Production cross-sections will remarkably increase at LHC energies, allowing to access bottomonium resonances in heavy ion collisions. In addition, the large statistics of charmonium events will allow to study the J/Psi polarization and J/Psi elliptic flow. The ALICE experiment will measure quarkonia in the central (|η|<0.9) and backward (-4.0<|η|<-2.5.) rapidity domains, combining electronic and muonic channels. Individual studies of each bottomonia resonance (  (1S ),  (1S ) and Υ (3S ) ) will be performed. The sensitivity of ALICE detector to different suppression scenarii will be presented. 295. Proton-proton Physics in ALICE Tapan K. Nayak a for the ALICE Collaboaration aCERN, Geneva, Switzerland; [email protected] We present the prospects for studying p-p physics in the ALICE experiment at the Large Hadron Collider(LHC). A complete understanding of the reaction mechanism governing p-p collisions at LHC energies comes from studying the bulk properties of the produced particles. Some of the physics topics [1,2] include the study of particle multiplicity, particle spectra, strangeness production, particle correlations, heavy-°avour production, photon and di-lepton production, quarkonia physics, production of bottom and charm quarks as well as jet studies. Study of the 1 ALICE – A Large Ion Collider Experiment 2 LHC – Large Hadron Collider 144 underlying event structures of high multiplicity events produced in p-p collisions will be of interest. In addition, ALICE will be able to explore non-perturbative strong-coupling phenomena related to confinement and hadronic structure at the new range of energies and Bjorken-x values accessible at the LHC. The primary objective of ALICE is to study the physics of strongly interacting matter and the quark-gluon plasma in heavy-ion collisions. The unique features of the experiment are the particle identification over a broad momentum range, powerful tracking with good resolution from 100 MeV c-1 to 100 GeV c-1 and excellent determination of primary and secondary vertices. For these reasons, ALICE is also ideally suited to study bulk properties of particles produced in p-p collisions. In this respect, the p-p programme of ALICE also forms an important benchmark for heavy-ion physics. Preparations for the data taking using the first p-p collisions from LHC are underway with hardware commissioning of the experiment and offline readiness. A physics data challenge to produce 100M p-p events, starting with variants of PYTHIA event generator, and processed through the ALIROOT simulation package [3] is in progress. These events are being analyzed to study the performances of the detectors for the p-p physics topics outlined above. Details of the performances and expectations for the p-p physics at LHC energies will be presented. References [1] ALICE: Physics performance report, volume I (ALICE Collaboration), J. Phys. G30(2004) 1517. [2] ALICE: Physics performance report, volume II (ALICE Collaboration), CERN/LHCC 2005-030, Dec 2005, to be published in J. Phys. G. [3] ALICE technical design report of the computing (ALICE Collaboration), CERN-LHCC-2005-018, Jun 2005. 1On leave from VECC, Kolkata, India 296. Equation of State Study in U+U collisions at CSR H.S. Xua for the CSR-ETF group of Modern Physics, Chinese Academy of Sciences Lanzhou, Gansu 730000, P.R. China, [email protected] aInstitute In high-energy nuclear collisions at RHIC, the partonic degrees of freedom dominate the early stage dynamic evolution. Now the question is at what collision energy, the dominating degrees of freedom return to the hadronic. In order to answer this important question, an energy scan program from s = 200 GeV to about 2 GeV have been discussed at both RHIC and future CBM at FAIR communities. In this talk we discuss the equation of state properties in U+U collisions at s 1.65 GeV. The BUU model is used in our calculations. This collision will become possible at the newly constructed accelerator in Institute of Modern Physics. Since the uranium is naturally deformed, the maximum density reached in such collision will depend on the relative orientation of the colliding nuclei. The maximum energy density is about 3 times of the ground state energy density. We also find that the duration of the system is much longer in the tip-tip* collisions compared with the body-body** collisions. The event anisotropy parameter v2; pT - spectra and the event-by-event ratio of nucleon over pion will also be discussed in different orientations. All of the observables will be measured in the proposed external target facility (ETF) at CSR. *Head on collisions along the long axis. **Head on collisions along the short axis 297. The Inner Tracking system of ALICE G.J.L. Nooren a for the ALICE-ITS collaboration of Physics, Utrecht University, P.O.B 80000 3508 TA Utrecht, the Netherlands, [email protected] aDepartment The Inner Tracking System (ITS) of ALICE consists of six silicon layers. The two innermost (SPD) starting at 4 cm from the beam, are made of pixeldetectors . The middle layers (SDD) 145 contain silicon driftdetectors, whereas the two outer layers are made of double-sided silicon stripdetectors with the outermost located at 43 cm radius. The ITS has 0.07 radiation length in the active region and a total mass of 150 kg. The purpose of the ITS is: a) determination of the vertex, b) reconstruct secondary vertices, c) track and identify low momentum particles, and d) improve angle and momentum resolution of particles that also traverse the TPC. The construction of the ITS is well advanced and its status will be presented. Prototypes of all detectors have been tested in several campaigns at CERN. The results of these tests have shown performance fulfilling the ALICE requirements. A simultaneous test of prototypes of all three subdetectors has demonstrated the integration with trigger and data-acquisition and has shown the electrical compatibility. The mechanical integration both between the subdetectors and with the TPC was exercised with mechanical prototypes and has led to a feasible integration scenario. It all shows that the system is ready for installation by the end of 2006. 298. Heavy-Ion Physics with the CMS detector at the LHC Russell Betts for the CMS Collaboration University of Illinois, Chicago, Chicago, IL, USA, E-mail [email protected] The Large Hadron Collider at CERN will collide protons at s = 14 TeV and lead ions at s NN = 5.5 TeV. The research program of the Compact Muon Solenoid (CMS) experiment includes a strong heavy-ion physics agenda, specially competent in the measurement of hard processes which have arguably provided the most exciting results at RHIC. The high center-of-mass energies available at the LHC will allow high statistics studies of high-density QCD with hard probes: heavy quarks and quarkonia with an emphasis on the b and Υ, high pT jets, direct photons, as well as Z0 bosons. The contribution of CMS to the LHC heavy-ion program provides a number of unique capabilities including: (i) Very large acceptance at midrapidity (η < 2.5, full φ) for layered detection of charged and neutral hadrons as well as muons, electrons, and photons over a wide range of pT . (ii) The best mass resolution of any LHC detector for Quarkonia (J/ψ,Υ) leading to clean separation of the various states and improved signal over background, as well as an excellent charged track momentum resolution over a wide range of acceptance. (iii) Full electromagnetic and hadronic calorimetry since day-1 for complete jet triggering and reconstruction over η < 3.0, with a large statistical significance for single jet and jet+X channels (X = jet, γ, Z), and for full b- and c- jet identification. (iv) Unparalleled forward physics (low-x QCD) capabilities thanks to the forward hadronic calorimeter HF (3< |η| <5), Castor-Totem (5.5< |η| <6.6), and the ZDC (|η| >8.1 for neutrals). (v) A DAQ system capable of delivering almost every Pb+Pb event to the High Level Trigger allowing maximum flexibility to select rare probes at the highest multiplicities expected at the LHC. In addition to the detailed studies of hard probes, CMS will measure charged multiplicity, energy flow and azimuthal asymmetry in an event-by-event basis. Detailed studies of the CMS capabilities and physics reach for different high-density QCD observables, using the full detector simulation and reconstruction will be presented. 299. Minimum Bias and Underlying event measurement with CMS detector from startup Livio Fanó for the CMS Collaboration INFN Perugia, Perugia, Italy, E-mail [email protected] The potential of the CMS experiment to study the minimum bias proton-proton collisions at the LHC start up for s = 0.9 TeV, and the underlying event in nominal conditions for s = 14 TeV is described. Methodologies to measure the charged multiplicity in different pseudorapidity regions are presented, along with a strategy for the early alignment of the CMS tracking detectors using minimum bias events. The underlying event is studied by examining charged particles in the region 146 transverse to jets and in the central region of Drell-Yan muon-pair production. 300. Triggering on Hard Probes in Heavy-Ion Collisions with the CMS Experiment at the LHC Gunther Roland for the CMS Collaboration Massachusetts Institute of Technology, Cambridge, MA 02139, USA, [email protected] Studies of heavy-ion collisions at the LHC will benefit from an array of qualitatively new probes not readily available at lower collision energies. These include fully formed jets at ET > 0 50 GeV, Z ’s and abundantly produced heavy flavors. For Pb+Pb running at LHC design luminosity, the collision rate in the CMS interaction region will exceed the planned event rate to mass storage by several orders of magnitude. Therefore an efficient trigger strategy is needed to select the few percent of the incoming event stream containing the most interesting signatures. This will be crucial for collecting statistically significant samples of the rarest probes, like Z0’s, and to facilitate highly differential studies of more common processes. The CMS experiment has developed a unique trigger system for high luminosity p+p running, dealing with event rates of 40 MHz using a two-layer trigger architecture. The first layer (“Level-1”) is implemented using custom electronics and provides a trigger decision based on local data from the calorimeter and muon systems. The second layer, the High Level Trigger (HLT), is implemented using a large cluster of commodity computers. At the HLT, the full information for each event accepted by the Level-1 is available, allowing for “offline” algorithms to be run for making the final trigger decision on each event. In this talk, we will present on overview of the trigger channels and productions rates considered for the CMS heavy-ion trigger studies and describe our trigger strategy. We will show that the DAQ and trigger architecture allows us to run a large selection of offline reconstruction algorithms on each Pb+Pb event occuring in the interaction region, at full luminosity, thus maximizing the CMS physics reach in heavy-ion running. 301. Exotic physics at the LHC with CASTOR in CMS Edwin Norbeck for the CMS Collaboration University of Iowa, Iowa City, IO, USA, E-mail [email protected] Co-authors: Yasar Onel (University of Iowa), Apostolos Panagiotou (University of Athens), Ewa Gladysz-Dziadzius, (IFJ, Krakow) CASTOR will extend the seamless electromagnetic and hadronic calorimetric coverage of CMS from |η| < 5.2 out to |η| < 6.6 (0.8° to 0.1°). Although the angular coverage is small, a substantial part of the reaction energy goes into CASTOR. This tungsten-quartz calorimeter is divided azimuthally into 16 segments and longitudinally into 70 sampling units, which are grouped into larger readout units. Although the main function of CASTOR is to more fully characterize interesting events in CMS, its detailed subdivision allows identification of exotic phenomena that have been predicted to occur only or primarily for this angular range. For heavy-ion reactions, this includes “strangelets”, which are metastable, almost neutral, objects with nearly equal numbers of s, u, and d quarks. Such matter is believed to form the core of neutron stars. “Centauros” or “disoriented chiral condensates”, whose nature has not been understood so far, would appear in CASTOR as unusual ratios of electromagnetic to hadronic components. Also, at these angles and energy, the gluons are expected to overlap to form a classical field known as a “color glass condensate”. If magnetic monopoles are made at the LHC, their initial kinetic energy is likely to be small, even with 1144 TeV Pb+Pb collisions. However, the monopoles would gain sufficient energy from the 4 T magnetic field of CMS to produce large, easily recognizable signals in CASTOR. If exotic objects are produced at the LHC, we will be able to recognize and study them. Their absence would be evidence that the exotic events seen in cosmic rays are not caused by energetic nuclei interacting with the atmosphere, but that the primary particles themselves are exotic. In any case CASTOR will provide, for the first time, a much-needed calibration for cosmic-ray air-shower detectors. 147 302. A Zero Degree Calorimeter for the ATLAS Experiment a S. N. Whitea Department of Physics, Brookhaven National Laboratory,Upton, N.Y. 11973, USA, [email protected] We present the design of the Zero Degree Calorimeter (ZDC) that we are proposing to build for the ATLAS experiment at the LHC. The ZDC consists of modules with Tungsten/quartz rod sampling and features full x,y coordinate readout of the showers. We discuss the unique physics capabilities of this design which allows measurement of both centrality and reaction plane in Pb-Pb collisions. In addition,π0 and other neutral hadrons can be reconstructed in the calorimeter, permitting study of large rapidity hadron production in pp, pA and AA collisions. We will also present results of radiation damage studies and performance in a high energy test beam. The project has been reviewed by the ATLAS collaboration with a final recommendation expected in October ’06. [1] ZDC group: G. Atoian, A. Denisov,V. Issakov,H. Kaspar,A. Poblaguev,S. White and M. Zeller. 303. New results and perspectives on RAA measurements below 20 GeV CM-energy at fixed target machines Z. Fodora, A. Lászlóa and G. Vesztergombia, for the NA49 Collaboration Research Institute for Particle and Nuclear Physics Budapest, H-1121 Konkoly-Thege M. u. 29-33., Hungary, e-mail to:[email protected] aKFKI Measurements of high pT pion, kaon and proton production play a central role in the understanding of AA, pA and pp interactions. The cleanest signature for jet-quenching is provided by the measurement of the nuclear modification factor RAA. Latest NA49 results ([1], [2]) at 158 GeV on RCP comparing central collisions relative to peripheral ones indicate a picture which is qualitatively similar to the RHIC at a somewhat weaker scale. In order to better understand the picture one needs high pT pp, and pA data to be able to disentangle the Cronin- and jet-quenching effects. High statistic high precision pp data on charged pion production was published by the NA49 collaboration ([3]) up to pT of 2:2 GeV=c. By accepting reduced accuracy the pT range can be increased at least by 0:5 GeV=c. As in the case of RHIC experiments one can compare the pp and AA particle yields in exactly the same detector which will minimize the systematic effects. The present pp statistics is surely not enough to go above 3 GeV=c in pT . It will be shown how far one can go in the near future using the upgraded NA49 detector at 17.3 GeV CM-energy. Assuming the existence of an effect of transverse spectra modification at 17.3 GeV, one is wondering: is there a threshold energy somewhere at lower value? In the long-run the FAIR accelerator is planned to provide at the CBM-detector 1010 proton/sec beam intensity upto 90 GeV energy. This unprecendented luminosity provides a unique possibility to extend the pT range into practically unknown territory. The perspectives of these extreme luminosities will be discussed. References [1] A. László, T. Schuster (for the NA49 Collaboration), Quark Matter 2005 parallel section proceedings, arXiv:nucl-ex/0510054. [2] T. Schuster, A. László (for the NA49 Collaboration), Proceedings of the 9th International Conference on Strangeness in Quark Matter, arXiv:nucl-ex/0606005. [3] C. Alt et al. (the NA49 Collaboration), Eur.Phys.J. C45 (2006) 343-381, arXiv:hep-ex/0510009. 304. RESULTS FROM THE ALICE TEST TPC aDepartment P. Christiansena for the ALICE TPC COLLABORATION of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden. The ALICE TPC is the largest and most complex TPC ever built[1]. The 550k readout channels, each capable of sampling the electric charge collected on the pads at 10 MHz, allow 500 million charge samples of the 88m3 drift volume. The TPC is designed to cope with up to 20,000 charged primary and secondary particles corresponding to an occupancy of up to 40% at the innermost radii. 148 Novel front-end electronics were developed which are capable of performing digital filtering and baseline correction of the signals. A TPC test setup was built at CERN where the performance of an ALICE TPC Inner Readout Chamber in combination with the electronics was tested using cosmic triggers and the PS T10 test beam facility. Based on these data the front end electronics performance has been studied in a high track density environment similar to that which is expected at LHC[2]. The space point resolution and particle identification power, via dE/dx, have been determined; Furthermore, the cluster charge straggling functions have been measured for different beta-gamma and compared to theoretical calculations from[3]. The results presented have been accepted for publication[4]. References: [1] ALICE Collaboration, ALICE TDR 7, CERN/LHCC 2000-001. [2] B. Mota et al., Nucl. Instrum. Meth. A 535, 500 (2004). [3] H. Bichsel, Nucl. Instrum. Meth. A 562, 154 (2006). [4] D. Antończyk et al., accepted for publication in Nucl. Instrum. Meth. A. 305. STUDY OF HADRONIC RESONANCES IN ALICE A. Badaàa, R. Barberaa,b, F. Blancoa,b, G. Lo Rec G.S. Pappalardoa, A. Pulvirentia,b,1, F. Riggia,b for the ALICE Collaboration (a) INFN - Sezione di Catania, Via S. Sofia, 64 - I-95123, Catania (Italy) (b) University of Catania - Department of Physics and Astronomy.Via S. Sofia, 64 - I-95123, Catania (Italy) (c) CNAF - Viale Berti Pichat 6/2, I-40127 Bologna (Italy) ALICE is one of the approved experiments at the CERN Large Hadron Collider. Its main purpose is to investigate the properties of hot and dense hadronic matter obtained in ultrarelativistic heavy-ion collisions (Pb-Pb at 5.5 ATeV), with the aim of evidencing the signatures of a phase transition to a quark-gluon plasma phase (QGP). Hadronic resonances are quark bound states whose lifetime (few fm/c) is of the same order of magnitude of the lifetime of the fireball. Even in absence of a phase transition, modifications of the properties of hadronic resonances can arise due to their interactions with the fireball medium [1, 2]. In particular, studying resonances allows to probe the time evolution of the source from chemical to kinetic freeze-out and test different hadronization scenarios [3]. Moreover, the combined investigation of resonances with strange quark content, such as the K∗(892) and Λ(1520) is also important due to the expected overall strangeness enhancement in heavy-ion collisions [4]. Our study aimed to investigate the ability of the ALICE detector to reconstruct K∗(892)0 and Λ(1520) resonances. Results will be presented from an analysis of p-p and Pb-Pb collisions (respectively at 14 TeV and 5.5 A TeV) simulated and fully reconstructed in a realistic ALICE environment scenario. Resonances have been reconstructed by means of the invariant mass analysis of their charged decay products (K∗(892)0 → πK and Λ(1520) → pK). Particular care has been devoted to the evaluation of combinatorial background, which turns out to play an important role in such study. References [1] E.V. Shuryak and G.E.Brown, Nucl. Phys. A717 (2003), 322. [2] R.Rapp, Nucl. Phys. A725 (2003), 254. [3] J. Letessier et al., J. Phys. G27 (2001), 427,G.Torrieri and J.Rafelski, Phys.Lett. B509 (2001), 239. [4] J.Rafelski and B.Muller, Phys.Rev. Lett. 48 (1982), 48,Phys.Rev. Lett. 56 (1985), 2334. 306. "Heavy-Ion Physics with the ATLAS Detector at the LHC" Authors: Speaker (to be determined) and Laurent Rosselet Departement de Physique Nucleaire et Corpusculaire (DPNC) Universite de Geneve, [email protected] The ATLAS experiment is designed for the study of proton-proton collisions at the CERN LHC. We report on an updated evaluation of the ATLAS capabilities to study heavy-ion physics. Most of 149 the detector subsystems retain their nearly full capability even in the presence of high-multiplicity soft background from nucleus-nucleus collisions. These studies show that, in addition to "day-one" measurements such as global observables and elliptic flow, heavy-quarkonia suppression and jet quenching, which provide crucial information about the formation of a quark-gluon plasma, are accessible to ATLAS. 307. DETECTOR EFFICIENCY EVALUATION USING DEAD ZONE REMOVAL BY FIDUCIAL CUTS E.T. Atomssa Laboratoir Leprince Ringuet, Ecole Polytechnique, Palaiseau, 91128, France, [email protected] A method for the estimation of detector acceptance and effciency for J/ψ analysis using the central spectrometer data sample from PHENIX Run4 AuAu collisions is described. This method handles certain types of ineffciencies, mainly those caused by electronics failures, which are run dependent and cannot be easily treated by general methods such as introducing response functions. It is based on the application of fiducial cuts over dead detector zones in simulation, and the manual removal of exactly the same dead zones in real data during signal counting. This requires a careful consideration of the causes of dead zones in real data, in order to avoid reducing the detector acceptance unreasonably. The method is finally cross checked by comparing distributions of parameters between real data and simulation after the application of the selected fiducial cuts on both. The major advantage of this method is its applicability at the late stage of the analysis/simulation and its fast turn around time, allowing for a more detailed control over systematics related to run dependent detector ineffciency. 308. A Study of the Intrinsic Time Resolution of MRPC Used in STAR-TOF Ming Shao (for STAR TOF group) Department of Modern Physics, The University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China, [email protected] Time-Of-Flight (TOF) based on Multi-gap Resistive Plate Chamber (MRPC) detectors had been successfully operated at the STAR experiment since 2003 [1] [2]. The MRPC time resolution is however found to be significantly larger (80-90ps [1, 3]) than that previously obtained in beam test (60ps) [4]. In order to fully understand MRPC working principles and operating requirements, an extensive calibration study is performed using data collected by STAR in 200GeV Au+Au collisions in 2004. The relation between MRPC timing, signal amplitude, hit position, incident angle, as well as particle species and momentum, are discussed in detail. Contributions from tracking properties of STAR-TPC are also studied by simulation. The intrinsic time resolution of MRPCs used in STAR-TOF, after taking all factors into consideration, is found to be in good agreement with beam test results. References: [1] Jian Wu, B. Bonner, et al., Nucl. Instr. & Meth. A 538 (2005) 243 [2] J. Adams, et al., (STAR), Phys. Lett. B 616 (2005) 8; J. Adams, et al., (STAR), Phys. Rev. Lett., 94 (2005) 062301 [3] STAR TOF group, ”TOFr Performance in RHIC Run-IV”, USTC workshop, 2004 Oct., Hefei, China [4] B. Bonner, G. Eppley, J. Lamas-Valverde, et al., Nucl. Instr. & Meth. A 478 (2002) 176; M. Shao, L.J. Ruan, et al., Nucl. Instr. & Meth. A 492 (2002) 344. 309. A barrel TOF for STAR at RHIC J. Wu* for the STAR Collaboration * Department of Modern Physics, University of Science and Technology of China Hefei, Anhui 230026, P.R. China, [email protected] With the successful runs of the MRPC-based TOF prototypes in STAR for the past several years, a full barrel TOF is being built to take part in data taking in late 2008. Since the beginning of 150 RHIC, STAR had repeatedly demonstrated its powerful and unique advantage: Large Acceptance. Together with other sub-detectors in STAR this TOF will greatly enhance the reach of the STAR scientific program significantly by extending the PID capability. It will allow STAR to extract the maximum amount of information available from soft physics measures on an event-by-event basis. It will also extend its power to the heavy flavor sector by increasing the signal to noise ratios for charm hadron reconstructions forD^0$,$D^+$,$D_{s}^+$,$J/psi\$, enabling STAR to make
systematic studies of charm thermalization and charm meson flow. In this talk, the physics results
achieved by the TOF prototypes as well as the goal of the full TOF expectable are presented. Also
explained is the progress of the TOF project accomplished so far.
310.
CONSTRUCTION AND EXPECTED PERFORMANCE OF THE HADRON BLIND
DETECTOR FOR THE PHENIX EXPERIMENT AT RHIC
a
Itzhak Tserruyaa
Weizmann Institute of Science, Rehovot, Israel, [email protected]
We describe the Hadron Blind Detector (HBD) that has been developed as an upgrade for the
PHENIX experiment at RHIC. The main purpose of the HBD is to allow a precise measurement of
electron-positron pairs from the decay of the light vector mesons and the low and intermediate mass
continuum in central Au+Au collisions. The HBD is a Cherenkov detector operated in pure CF4. It
consists of a 50 cm long radiator directly coupled, in a windowless configuration, to a triple GEM
detector, with a CsI photocathode evaporated on the top face of the first GEM, followed by pad
readout. A comprehensive R&D program has been carried out to demonstrate the validity of this
novel concept and a full-scale prototype has been constructed and tested. The final detector
construction is nearing completion with installation foreseen in time for the next RHIC run in the
fall of 2006.We review the entire project with emphasis on the most recent achievements. In
particular we describe construction techniques, present test results, and discuss the expected
performance, of the HBD.
311.
A Heavy Flavor Tracker for STAR
A. Rosea for the STAR Collaboration
Berkeley National Laboratory, 1 Cyclotron Rd. MSTP-70R0319 Berkeley, CA,94720, USA,
[email protected]
aLawrence
To understand the partonic EOS of matter in relativistic heavy ion collisions, it is necessary to
study both the collectivity of the produced matter and the degree of thermalization. Direct
reconstruction of heavy flavor hadrons can be used as a tool to elucidate these properties of the
matter formed in such collisions. As the current STAR experiment does not have the capability to
make detailed observations of these properties, it has just designed an upgrade to its tracking
capability. A new tracking detector, called The Heavy Flavor Tracker (HFT), provides an
unambiguous measurement of charm hadrons through the direct reconstruction of their hadronic
decays. It achieves this tracking accuracy by measuring high accuracy space points near the
collision vertex. The HFT uses a novel CMOS based technology called Active Pixel Sensors, which
has a pixel pitch of 30 µm and a thickness of 50µm. This design allows for a low mass and high
resolution detector. We will present the HFTs design, and also discuss its expected performance. In
addition, we will provide rate estimations for both D0 v2 and RAA measurements.
312.
COMMISSIONING OF THE ALICE TPC
L.Musa for the ALICE Collaboration
CERN, Physics Department, Geneva, CH-1211, Switzerland, [email protected]
The main tracking detector of the ALICE experiment at the LHC is a large TPC. This detector,
with a field cage manufactured of carbon fiber composites with total volume of 95 m3, and 36
sectors of read-out chambers installed at the end plates of the cylinder, has now been fully
151
assembled and is undergoing commissioning with cosmic rays and tracks produced by a UV laser
system. The system comprises a custom-designed electronic read-out based on a low noise
preamplifier/shaper chip, and a digital circuit with a 10-bit 10-Msps ADC integrated into one chip
for all 560000 read-out channels. We will report on the status of commissioning including analysis
of the quality of track reconstruction and results on drift velocity, electron diffusion and position
resolution of thetracking chambers as well as on the overall performance parameters of the detector.
152
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