Hadron Spectra in Au Au Collisions by STAR Experiment at RHIC

1
Hadron Spectra in AuAu Collisions by STAR
Experiment at RHIC

• Masashi Kaneta
• for the STAR collaboration
• LBNL

2
Introduction

• Study of bulk properties
• Macroscopic approach
• Chemical freeze-out
• Thermal freeze-out
• Focusing on pT distribution
• Thermal freeze-out Temperature
• Transverse flow

Expansion Cooling
Time
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RHIC-STAR experiment

• Solenoidal Tracker At RHIC

40 Institutes/Universities 300 Collaborators

• One of large experiments at RHIC
• 2p acceptance
• Excellent particle identification

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STAR Event
Tracks are reconstructed by online tracking
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Particle Identification

• dE/dx by TPC p,K,p,d,He,
• Kink method K
• RICH 1-3 GeV/c for p/K, 1.5-5GeV/c for p
• Topology L, X, W, K0s
• Combinatrics D, L, L(1520), K, f,

• TOF (year 2)
• EMC (year 2)

p
K
dE/dx
p
e
p/Z GeV/c
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pT Distribution / Kinetic Freeze-out

• Kinetic freeze-out
• End of elastic interactions
• Information of momentum is frozen
• Boltzmann distribution flow effect

Blast wave model E. Schnedermann et al.,
PRC48(1993)2462
Boosted
No Boost
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pT distribution vs. Centrality
ltNpartgt for p 345?7 289?9 221?4 152?9 102?4
63?4 35?3 20?2 9?4 -------
ltNpartgt for K, p 345?7 280?9 235?8 180?9 135?8 100
?4 70?4 25?3
STAR Preliminary
K- (dE/dx)
K- (kink)
p
p
central peripheral
p-
K (kink)
K (dE/dx)
pT GeV/c
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Centrality dependence of T th and ltbrgt

• Selected similar centrality region in p and K,p

p-
K
K-
p
p
38 115 224 347 ltNpartgt
pT GeV/c

• As a function of centrality
• Tth 100 MeV
• ltbrgt goes up then saturated
• Flow profile changed?

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Bombarding Energy Dependence

• From SPS to RHIC
• Increasing flow
• Decreasing temperature
• Longer time for cooling at RHIC?

STAR
PHENIX
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Summary

• The pT distributions of p, K, and p are obtained
  as a function of centrality from RHIC-STAR at
  ?sNN130GeV AuAu
• The blast wave model describes the data over all
  of centrality
• As a function of centrality at RHIC
• Tth 100 MeV
• ltbrgt goes up then saturated (0.55c)
• Flow profile changed?
• From SPS to RHIC
• Increasing flow
• Decreasing temperature
• Indicating longer time for cooling at RHIC?

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STAR vs. PHENIX
p-

• PHENIX p and K show smaller yield at pTgt0.6 than
  STAR
• upto factor of 2!!
• Protons have coincidence

K-
K
p
p
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Centrality
centrality bin for kink K
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STAR Event
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Test of Flow Profile