Download Résultats récents du RHIC

Résultats récents du RHIC
Outline : (1) heavy quarkonia production;
(2) jet – medium interactions in heavy ion collisions;
(3) correlations and fluctuations;
(4) forward and central flow;
(5) searching for gluon saturation;
(6) W/Z measurements.
Guy Roche, LPC-Clermont.
Etretat, 20-23 Septembre 2010.
p.1
1) heavy quarkonia production.
From Daniel Kikota for the STAR colaboration, ICHEP 2010.
baseline:  in p+p 200 GeV
Consistent with CEM, (inconsistent with CSM: ~ 2)
Consistent with world data trend
p.2
Cold nucl. matter:  in d+Au
Cold nucl. matter:  in d+Au
RdA  0.78  0.28(stat.)  0.20(sys.)
Consistent with Nbin scaling.
Cold Nuclear Matter effects (shadowing) are rather small.
p.3
 in Au+Au 200 GeV
4.6 significance, 95 Signal counts in 8 < m < 11 GeV/c2
Includes , Drell-Yan + b b
Analysis in progress
p.4
Summary
 High-pT J/ψ measurement in p+p - a crucial test of quarkonia production
in QCD.
 (B  J/ψ / J/ψ = (13 ± 5)% for pT > 5 GeV/c.
 No J/ψ suppression at high-pT in Cu+Cu 200GeV: RAA ~ 1
 First  cross section measurements at RHIC energies:
- p+p results consistent with Color Evaporation Model
- d+Au: RdAu = 0.78 ± 0.28 (stat.) ± 0.20 (sys.)
p.5
(2) jet – medium interactions in heavy ion
Collisions.
From Olga Evdokimov for the STAR colaboration, ICHEP 2010.
Angular pair-correlations
84-93%
proton-proton
Δρ
ρref
φΔ
28-38%
74-84%
ηΔ
18-28%
64-74%
STAR
Preliminary
9-18%
55-64%
46-55%
5-9%
0-5%
Evolution of several correlation structures is observed
Shown are 200 GeV minimum bias Au+Au data.
Similar analysis performed for 200 GeV Cu+Cu, and 62 GeV Au+Au and Cu+Cu data.
p.6
Di-jets through correlations
assoc.
trig2
trig1
Trig1 is highest pT particle in event with 5-10 GeV/c
Trig2 (pT > 4 GeV/c) is back-to-back with Trig1
Associated particles pT > 1.5 GeV/c.
200 GeV Au+Au and d+Au.
same-side
away-side
STAR Preliminary
No
evidence of medium modifications
associated particle
pT spectra
Di-jets observed - all tangential?
p.7
Jet-energy calibrarion
Direct γ-hadron correlations
STAR Preliminary
 rich sample has lower near-side  Similar medium effect on the awayyields compared to those of the
0  different bias
side of 0 and dir
 is this due to tangential emission?
p.8
Inclusive jet measurements
Central Au+Au: background correction leads to a factor of 2 uncertainty in cross-section
p.9
3) Correlations and fluctuations.
From Terence J Tarnowsky for the STAR collaboration, Winter Workshop on
Nuclear Dynamics 2010.
F-B Multiplicity Correlations
•
•
•
Predicted in context of Dual Parton Model [DPM] (and Color Glass
Condensate [CGC]).
Test of multiple elementary [partonic] scattering.
Linear expression relating Nb and Nf (forward and backward
multiplicity), found in hadron-hadron experiments (ex. UA5),
 N b  ( N f )  a  bN f
•
“b” is correlation strength.
– Function of √s and A.
– Coefficient can be
expressed as,
b
N = # of hadrons
 N f N b    N f  N b 
 N    Nf 
2
f
2

Dbf2
D 2ff
p.10
F-B Correlations
•
Central 200 GeV
Au+Au collisions
show a strong longrange correlation.
•
Most peripheral
Au+Au have
negligible LRC, as
does pp.
•
HIJING and
Parton String
Model (PSM) do
not agree w/
Au+Au data.
•
Multiparton
interaction in
central Au+Au
collisions.
•
See talk by M.
Skoby.
Phys.Rev.Lett.103:172301,2009
p.11
Characterize Fluctuations
•
NA49 uses the variable dyn
2
2
2
2
 dyn  sign  data
  mixed
  mixed
  data
 is relative width of K /  distribution
•
Measure deviation from Poisson behavior using dyn
 dyn,K 
•
N K N K  1
NK
2

N N  1
N
2
N K N
2
N K N
It has been demonstrated (for K/p and p/p) that,

2
dyn
  dyn
p.12
Excitation Function for σdyn,K/π
STAR central Au+Au (0-5%) collisions with SPS central Pb+Pb collisions
(0-3.5%).
Phys.Rev.Lett.103:092301,2009
• Large decrease in
fluctuations as function of
energy from NA49.
• Fluctuations measured by
STAR approximately
constant as function of
energy from 19.6-200 GeV.
•  : 0.2 < pT < 0.6 GeV/c
•K: 0.2 < pT < 0.6
GeV/c
p.13
4) Forward and central flow.
From Eric Richarson for the PHENIX collaboration, RHIC & AGS Annual
Users Meeting June 7-11, 2010 BNL.
v2, v4 h± Results
•
•
•
•
RP detectors with different 
ranges yield similar signal
Signal varies v2 (v4)
– mid-central ~5% (10%)
– central/peripheral 10% (20%)
Signals agree within systematic
errors (v2 = 10%, v4 = 20%)
Indicates reliable measurement
largely free of  and pT dependent
non-flow effects within the
measured range
(pT = 0.5 - 2.4
GeV/c)
arXiv:1003.5586
p.14
0-60% Centrality
v2, v4 h± Results
•
•
Fig (a) & (b)
– v2 and v4 signal have similar shape
Fig (c) - v4/(v2)2
– Ratio independent of pT within 0.5-3.6 GeV/c
– v4/(v2)2 ≈ 0.8 for ~50<Npart<200, which is
greater than ideal hydro (dot-dot)
– adding eccentricity fluctuations within hydro
model fits data better (dash-dash)
– Even better fit when  added to hadron gas
phase and small  added to QGP phase (dotdash)
– Ratio significantly increases Npart > ~200
– Additional fluctuations needed to match
central data (solid)
– Fit with data implies a small /s
Data gives strong indication of
hydrodynamic behavior in
matter created at RHIC
These precision measurements
should provide stringent
constraints for models.
p.15
Heavy Flavor v2 Analysis Footnotes
•
•
•
•
•
•
•
Run-4, ~700M evts
Measured heavy flavor using
single electrons from semileptonic
decays (~10% branching ratio)
Tracking done using DC, PC, RICH
and EMCal
RICH is primary electron identifier
Photonic electron bkgrd
subtracted using “cocktail
method” where background v2
was estimated using a Monte Carlo
simulation with input from
measured data
Photonic cocktail included
electrons from 0 and  decays
and  conversions and direct 
Electron v2 from K decays was
also subtracted
arXiv:1005.1627
arXiv:1005.1627
p.16
Heavy Flavor v2 Results
arXiv:1005.1627
•
•
•
Positive v2 at low pT - indicates heavy quarks (mainly charm) couple
with the medium.
Shape similar to lighter quarks except at highest pT.
Although errors are large at high pT the signal appears to fall
significantly from peak. This indicates a change in energy loss
mechanism or a growing contribution from the bottom quark.
p.17
Model Comparisons
•
•
•
All models include quark
coalescence
Models that best describe low
pT data are:
– Greco et al. with charm flow
– Zhang et al. with larger
charm quark partonscattering cross section ( =
10 mb)
– van Hees et al. with
resonance interactions
Indicates
– heavy quarks participate in
the medium
– Coalescence and resonance
are large contributors to HF
v2 at low pT
arXiv:1005.1627
p.18
5) searching for gluon saturation.
From Beau Meredith for the PHENIX collaboration, DIS Conference, Florence,
Italy, April 19-23, 2010.
Rapidity Separated Correlations : Widths.
2.0 < pT,trig< 3.0 GeV/c
trig 0 or h+/-,  = 0
assoc 0,  = 3.4
No significant broadening
between p+p and d+Au within
large experimental uncertainties
p.19
Rapidity Separated Correlations : IdA .
0.45 < pT,assoc < 1.59 GeV/c
trig 0 or h+/-,  = 0
assoc 0,  = 3.4
Increasing suppression of IdA
reaches a factor 2 for central
events indicating di-jet
suppression
peripheral
central
p.20
Forward/Forward Correlations : p+p .
•
Show per-trigger correlation functions, i.e. 1/NtrigdN/d(Df)
– Area of away-side peak represents conditional yield without efficiency correction
– More work needed to determine uncorrelated background level
– Conditional yields, widths not shown
Trigger particle pT > 2 GeV/c
Associate particle pT > 0.875 GeV/c
Data points mirrored for Df > 
trig cluster  = 3.4
assoc 0,  = 3.4
p.21
p+p vs d+Au Central .
Decorrelation and/or suppression seem to get stronger for central d+Au
collisions.
p.22
p+p vs d+Au Peripheral .
Peripheral d+Au collisions are more similar to p+p collisions
p.23
6) W/Z measurements.
From Mickey Chiu for the PHENIX collaboration, RHIC and AGS Users Meeting, June 7-11, 2010.
Comparison To Measured spectra
Data and MC driven BG estimation:
EMCal cluster distribution after
subtracting cosmic background
 (Conversion + Accidental)
 Tracking Acceptance
+
(NLO Hadrons thru Geant + FONLL c/b)
Normalization from fit to 10-20 GeV
+
-
•The same scale factor for PYTHIA was used for W/Z shape.
•W-e- signal has fewer counts than W+e+ signal as expected
p.24
Isolation cut
•Signature of a W event is that it is isolated
•Sum up energy in a cone around electron and in cone
on opposite hemisphere
+
E < 2GeV
-
•90+% of signal is kept (red histograms)
•Factor ~5 reduction in jet dominated region
p.25
From Joe Seele for the STAR collaboration, RIKEN BNL Research Center Workshop, June 24-25, 2010.
2009 Results
STAR Preliminary Run 9
In 2009 STAR recorded its first 500
GeV data set and extracted its first
mid-rapidity AL measurement.
Achieved S/B~11 for the W+ and
S/B~6 for W-
p.26
Expected Data
RHIC is planning to run 500 GeV
polarized p+p collisions in a multiyear effort to constrain the
polarization of the anti-quarks in
the proton
Calculations assume the
demonstrated S/B (6 and 11) for the
mid-rapidity projections and S/B~1 for
the forward and backward rapidity
projections
p.27
Back-up slides
p.28
Summary &Outlook from STAR:

Jet quenching discovered at RHIC has been extensively studied for years:
 Modification of angular shapes, production rates, transverse momentum and
energy distributions

Evolution of jet studies in HI:
 Inclusive hadron measurements → di-hadron correlations → multi-particle
correlations → full jets

Outlook:
 Towards “theory-ready” (partonic) energy loss measurements
 Disentangling experimental biases
p.29
ndyn,p/p, STAR and NA49
• dyn,p/ displays
strong system
size dependence
for small dN/d.
• Fit is to STAR
Cu+Cu 22.4
GeV data only.
• Interpretation
still under study.
p.30
RAAJet
Inclusive jet ratios
R=0.4
RAA of pions ~ 0.2
RAAJet> RAA: recover larger fraction of
cross-section, but not all
Significant ratio suppression wrt. pp
→ medium induced ET broadening
p.31
Excitation Function for σdyn,p/π
• Solid points are
data from STAR
or NA49.
• Open black
points are HSD
prediction from
Konchakovski, et.
al.
arXiv:0906.3229.
• Open red points
are UrQMD run
locally with
STAR
acceptance.
p.32