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-jet measurements
Table of Contents:
Motivation
Experimental Challenges
-trigger in Run 2007
Preliminary QA of -trigger Data
Shower Shape Analysis
Summary
Texas A&M Group
Ahmed M. Hamed
BNL 10-17-07
Why -jet measurements?
Motivation
Single Particle Spectra-RAA
Mid-rapidity
Statistical Method
Heavy quarks suppress as much as light quarks in the medium.
RAA exhibits only very limited sensitivity to the properties of the medium.
More differential observable is needed.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Motivation
Why -jet measurements? Jet-like azimuthal correlations
?
Near-side: p+p, d+Au, Au+Au
is similar.
Back-to-back: Au+Au strongly
suppressed relative
to p+p and d+Au.
Surface bias for the trigger particle.
Suppression of the backto-back
correlation in central
Au+Au is a final-state
effect
Trigger particle with no surface bias is required for better calibration
of the away-side jet.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Why -jet measurements?
Motivation
Summary
Four multipurpose experiments (BRAHMS, PHENIX, PHOBOS, STAR)
 Empirical lines of evidence:
Energy density well beyond critical value.
Large elliptic flow.
Jet quenching.
dAu control experiment.
 Interpreted in terms of a strongly coupled QGP and a new QCD state
(?) Color Glass Condensate
Required:
Better understanding for the energy loss mechanism!
oDirect Photons:
Doesn’t couple to the medium.
QGP thermal photons.
Elliptic flow.
Test for binary scaling for hard process.
Gamma-charged hadrons correlation.
Challengeable measurements!
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Motivation
Why -jet measurements?
LO Direct photons
direct component
schematic view
thermal:
e
 E /T
Decay photons
Bremsstrahlung
fragmentation component
oGamma-charged hadrons correlation.
 Calibrated probe of the QGP – at LO.
 No Surface Bias
 Hard process
hard:
1
pTn
 Possible discriminator for quark/gluon jet at LO.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Experimental Challenges
Is it possible to measure?
In medium:
0 –spectra are suppressed by a factor of ~5 relative to the
scaled p+p collisions.
The away-side in di-jet production is more suppressed.
Pythia v6.131 event
generator
pp-collisions at
√s=200 GeV,
|η|<1 (STAR
acceptance)
Background sources of direct photons suppressed in medium.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Experimental Challenges
Inclusive -jet
Is it possible to measure?
in Au+Au at s=200GeV
SIMULATION (pp)
0 simulation
STAR Preliminary
Simulation shows no associated particles
in -charged correlation.
photon simulation
Away-side decreases with increasing centrality.
Decrease in near-side due to the increased
fraction of prompt photons.
Need /0 discrimination.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Experimental Challenges
Is it possible to measure?
0 Bin
Mixed
 Bin
Reduction in near angle peak towards photon Bin.
Effect is more prominent for larger Ettrigger .
Away-side yield is reduced.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Experimental Challenges
Texas A&M Group
Is it possible to measure? cucu2005
STAR Preliminary
STAR Preliminary
STAR Preliminary
STAR Preliminary
Ahmed M. Hamed
BNL 10-19-07
Experimental Challenges
Texas A&M Group
Is it possible to measure?
Ahmed M. Hamed
BNL 10-19-07
Experimental Challenges
Is it possible to measure?
0 DECAY KINEMATICS
min= 2 Sin –1 (mInv /E),
 ~10-17 s
Towers (~0.05x~0.05),
Strips (~0.007x~0.007),
d ~2.2m at =0, l~2.93m.
-plane
Electromagnetic transverse
shower characteristics
0’s pT(GeV/c)
Texas A&M Group
High energy core.
Low energy halo.
Ahmed M. Hamed
BNL 10-19-07
L2 Gamma Trigger in Run 2007
oTower threshold
ET=5.76 [GeV]
oCluster threshold ET= 7.44 [GeV]
oCluster size is one or two tower.
L2gammaResult Contains: phi_bin,eta_bin, tower ET,
and Cluster ET.
~1.2M events. ~50% Reversed Full Field.
http://online.star.bnl.gov/L2gamma2007/l2gamma2007_bemc/
All runs after 8143* are in the reversed full field configuration.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Preliminary QA of -trigger Data- BEMC
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Preliminary QA of -trigger Data- BEMC
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Preliminary QA of -trigger Data- BSMD saturation
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Preliminary QA of -trigger Data- BEMC 0
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Preliminary QA of -trigger Data- Hot Towers
Tower_Id !=1433,3407,3711,3720,3840
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Showers shape Analysis
Real data vs. Single particle simulation
pp@2006
Shower shape is wider in real data than in simulation!
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Shower Shape Analysis
Real data vs. pythia
pp@2006
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Shower Shape Analysis
Real data vs. pythia
Saturation parameters-Eta [700,70,10]
Saturation parameters-Phi [700,70,10]
oPythia doesn’t reproduce the shower shape even with saturation!
oIn phi-plane the shower shape is closer to the real data than in eta.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Shower Shape Analysis
0 vs. electron
Saturation parameters-Eta [700,70,10]
Saturation parameters-Phi [700,70,10]
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Shower Shape Analysis
Texas A&M Group
0 vs. electron
Ahmed M. Hamed
BNL 10-19-07
Shower Shape Analysis
Texas A&M Group
0 vs. electron
Ahmed M. Hamed
BNL 10-19-07
Shower Shape Analysis
Texas A&M Group
0 vs. electron
Ahmed M. Hamed
BNL 10-19-07
Shower Shape Analysis
Texas A&M Group
0 vs. electron
Ahmed M. Hamed
BNL 10-19-07
Summary
-jet measurements are very promising tool for better understanding of the medium
Shower shape study is required for direct photons identification.
Promising study for transverse shower profile is undertaken.
Embedding request is still under processed.
Texas A&M Group
Ahmed M. Hamed
BNL 10-19-07
Motivation
Texas A&M Group
BEMC- 0 AuAu@2007
Ahmed M. Hamed
BNL 10-19-07