Zhangbu Xu, CIPANP2003 1 Global Observables & PID Spectra From STAR Global Observables: Gluon...
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Transcript of Zhangbu Xu, CIPANP2003 1 Global Observables & PID Spectra From STAR Global Observables: Gluon...
Zhangbu Xu, CIPANP2003 1
Global Observables & PID Spectra From STAR
Global Observables: Gluon Saturation Minijet Contribution Phase Transition
Effect of Dense Medium on Particle Production and Resonance Properties Identified Particle Production & pT Spectra Resonance Properties
Future Programs Conclusions
Zhangbu Xu for the STAR Collaboration
Zhangbu Xu, CIPANP2003 2
EOS?
Initial ? Final
L. Van Hove, PL 118B (1982) 138
Multiplicity&<pT> related to Initial Condition or Phase Transition? Hydrodynamics (collectivity) Thermalization/Equilibrium
Particle Production Identified Particle
Flow Effect/Recombination Particle Properties
in dense Medium
P. Kolb, et al
Zhangbu Xu, CIPANP2003 3
ColorGlassCondensate Qs
2 ~ s(xGA(x, Qs2))/(RA
2) dNch/d/(RA
2) Qs2/ s
dNch/d/Npart 1/ s
1. Relevant Scale: Qs2dNch/d/(RA
2)J. Schaffner-Bielich, et al. nucl-th/0108048; D. Kharzeev, et al. hep-ph/0111315
2. Gluon SaturationThermalization?A different view on the consequences of gluon saturation (A. Mueller, QM02)
Gluon Saturation
Zhangbu Xu, CIPANP2003 4
Effect of jet production on <pT>
Wang&Hwa PRD 39(1989)187
dNch/d = (1/2) Npartns
soft + nhNbinjet/in
hardminijet contribution
Zhangbu Xu, CIPANP2003 5
How to Probe Dense Matter?
Modification in medium
Decay quicklymatter exists 10-23s
Small or no FSIleptons, photons, neutrino
Golden: J/
q
q
l
l
s
Small Branching Ratio(10-4), Low Production Rate
Zhangbu Xu, CIPANP2003 6
Last Call for RHIC PredictionsNucl.Phys. A661 (1999) 205-260
Cleaner Way of Detecting Modification?
Hadronic Decay at Late Stage Lower Density Lower Temperature Smaller Effect Hadronic Decay Larger Signal Extrapolation
R. Rapp, et al.
J. Schaffner-Bielich, et al.
Zhangbu Xu, CIPANP2003 7
All that Matters: Cross-section
Different by 5Rescattering>Regeneration at later stageRedistribution of momentum drives flow
Chemical freeze-out
Kinetic freeze-out
K*
lost
K*
measured
K
K* K
K*
K*
K
K*
K K K*
measured
Zhangbu Xu, CIPANP2003 8
STAR Detector
ZCal
Barrel EM Calorimeter
Endcap Calorimeter
Magnet
Coils
TPC Endcap & MWPC
ZCal
FTPCs
Vertex Position Detectors
Central Trigger Barrel or TOF
Time Projection Chamber
Silicon Vertex Tracker
RICH
FPD FPD
Zhangbu Xu, CIPANP2003 9
Multiplicity reflects GeometryCentrality definitions:dNch/d, Impact Parameter, Participants
GeVsNN 130
Multiplicity &Transverse Spectra
dNh-/d|=0 = 280120dNch/d|=0 = 567 138
hminus:<pT>=0.508GeV/cpp: 0.390GeV/c
5.0||/
ddNh
ZDC cut
Zhangbu Xu, CIPANP2003 10
pT Centrality Dependence
200/130 ratio consistent with flat: both Nch and <pT>Nch ratio: 1.190.05 (sys)<pT> ratio: 1.00 0.02 (sys) Little centrality dependence
we see no increase of <pT> lose the early information?Maximum Missing Information thermalization?Dominant Soft Interaction Contribution?
Hydro, P. Kolb
HIJING
RQMDN. Xu et al. QM02
Zhangbu Xu, CIPANP2003 11
Characteristics of Mean pT
M. Szczekowski PRD 44 (1991) R577e+e-: along the thrust axis agrees with JETSET calculation (OPAL PLB320(1994)417)
AA: can not be treated as superposition of more elementary collisions
pp: can not be treated as superposition of more elementary collisions
e+e-: pure jets; pp: soft+hardAA: ???
2ch
ppTpp
AAAAT
πR/dηdNs
a)p(ssap
Zhangbu Xu, CIPANP2003 12
Summary I STAR Measures multiplicity and average
transverse momentum of charged particlessnn=200, 130 GeV
<pT> from AA has characteristic energy dependenceNOT simple superposition of more elementary collisions
Comparison with Models Saturation (no scaling between <pT> and Qs) Two- component (not enough <pT>) Transport Model (rescattering important)
Possible due to early interaction and thermalization
Zhangbu Xu, CIPANP2003 13
Identified Particles
Particle Yield pT Spectra
Flow Hard Interactions
In-medium Effect Resonance Properties
Zhangbu Xu, CIPANP2003 14
Dominant Particles SpectraDominant Particles Spectra
Measured from TPC dE/dxClear centrality dependence of spectra shape in pbar
STAR Preliminary
pp
Zhangbu Xu, CIPANP2003 15
Dominant Particles CentralityDominant Particles Centrality
STAR Preliminary, K, p mean transverse momentum <pT> increase in more central collisions;
2) Heavier mass particle <pT> increase faster than lighter ones as expected in hydro type collective flow.
3) Consistent with Nch within 1%
4)Particle ratios little centrality dependence
5)Scattering
Zhangbu Xu, CIPANP2003 16
p+p collisions (m.b.) All fit to thermal (T,T) = (0.17,0) Except
Au+Au collisions (5%) All fit to thermal (T,T) = (0.1,0.6c) Except TT= (0.17,0.3c)
- + + (10%)
<p<pTT> Mass Dependence> Mass Dependence
Partonic collectivity?Partonic collectivity?
Larger Flow Effects when• Larger Nucleus• Higher Beam Energies• Heavy ParticlesSPSRHIC Same Hadronic Phase, But higher flow?
Zhangbu Xu, CIPANP2003 17
Different Mass Particles
At pT ~ 2-3 GeV/c, yields approach each other. Heavier mass particles show stronger collective flow effects !
Zhangbu Xu, CIPANP2003 18
Similar Mass Particles
Spectra Different at Low pT (pT<1.5GeV/c)
Similar at higher pT
Reflect in <pT>1. Slightly different in <pT>
due to low pT2. Higher pT contribution is
significant3. shows larger flow
p,
Flow, recombination?
Zhangbu Xu, CIPANP2003 19
What Determines pT Spectra?
/K Independent of anything
non-interacting at hadronic stage?
STAR Preliminary
ppAuAu:
PowerLaw Mt Exponential
hard contribution thermal-like source?
Zhangbu Xu, CIPANP2003 20
Scattering Effects
Thermal Production
1. K*/K independent of Beam Energies (pp,e+e-)2. Low K* Production in AuAu
STAR Preliminary
Zhangbu Xu, CIPANP2003 21
Resonance Invariant Mass Distribution
STAR Preliminary
0.8 pT 0.9 GeV/c|y| 0.5
pp Minimum Bias Au+Au 40% to 80%
1.2 pT 1.4 GeV/c|y| 0.5
STAR Preliminary
K*0
*(1520)
STAR preliminary p+p at 200 GeV
, f0(980), , *(892), *(1385),*(1520), D*
++ --
Zhangbu Xu, CIPANP2003 22
Mass & Width of Resonances
Phase Space
Scattering
Interference
Modifications
STAR Preliminary
Zhangbu Xu, CIPANP2003 23
20M d+Au Minbias Events
Resonance Method:without secondary Vertex (statistical)
Future upgrade:
Micro-vertex detector (event-by-event)
D0Kπ D±Kππ
|y|<1, pT < 4 GeV/c|y|<0.25, 7< pT <10 GeV/c
Direct Measure of Open Charm
• Charm Production• ccJ/• Heavy Quark Energy Loss• Flavor Tagging
STAR Preliminary
Zhangbu Xu, CIPANP2003 24
MRPC TOF Barrel
Multi-gap Resistive Plate ChamberNew Technology, Low Cost(glass+fishing line), High Resolution (<100ps)One tray (1/120) prototype in d+Au run (2 month ago)
Hadron PID (proton up to 3GeV/c) (spectra, resonance,D) Electron PID (with TPC dE/dx) upto 3GeV/c
Full Coverage for dileptons (including , , J/)
Zhangbu Xu, CIPANP2003 25
Conclusions
Global Observables (Nch,<pT>): different behavior from elementary collisions
Large Flow Increase with beam energy, Nucleus Even particles with small hadronic
Spectra exhibit thermal production Possible Modification of Particle Properties Large Rescattering Effect on Resonance Spectra More rare, exciting probes to come
Zhangbu Xu, CIPANP2003 26
Soft and Hard Processes
Momentum Scale: Qs , p0 (~2GeV)
Soft: only depends on multiplicity (“sqrt”) Qs2 Nch?
Hard: energies, multiplicity (“linear”) Both have truth in them
0 10 20 30 40 charge multiplicity
0 10 20 30 40 charge multiplicity
CDF PRD 65 (2002) 072005
Et>1.1GeV
pp
minijets