Masashi Kaneta, LBL
Hadron Spectra in Au+Au Hadron Spectra in Au+Au Collisions Collisions
by STAR Experiment by STAR Experiment at RHICat RHIC
Masashi Kaneta for the STAR collaboration
LBNL
Masashi Kaneta, LBL
IntroductionIntroduction
• Study of bulk properties• Macroscopic approach
– Chemical freeze-out– Thermal freeze-out
• Focusing on pT distribution– Thermal freeze-out Temperature– Transverse flow
Tim
e
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Exp
ansi
onC
oolin
g
Masashi Kaneta, LBL
RHIC-STAR experimentRHIC-STAR experiment
• Solenoidal Tracker At RHIC~40 Institutes/Universities~300 Collaborators
• One of large experiments at RHIC
• 2acceptance• Excellent particle
identification
Masashi Kaneta, LBL
STAR EventSTAR Event
Tracks are reconstructed byonline tracking
Masashi Kaneta, LBL
Particle IdentificationParticle Identification• dE/dx by TPC : ,K,p,d,He,……• Kink method :K
• RICH : 1-3 GeV/c for /K, 1.5-5GeV/c for p
• Topology : K0s
• Combinatrics : ……
K
p
e
|p/Z| [GeV/c]
dE/d
x
• TOF (year 2)• EMC (year 2)
Masashi Kaneta, LBL
ppTT Distribution / Kinetic Freeze-out Distribution / Kinetic Freeze-out
• Kinetic freeze-out– End of elastic interactions– Information of momentum is frozen
• Boltzmann distribution + flow effect
tanh 1r
nRrpxf ssr /),(
)0 ,sinh ,(cosh )0,,( rezrtu
No Boost
Boosted
Blast wave model;E. Schnedermann et al., PRC48(1993)2462
Masashi Kaneta, LBL
ppTT distribution vs. Centrality distribution vs. Centrality
pT [GeV/c]
]G
eV/c
)[(
2
2-2
TT
dpdy
p
nd
K
(dE/dx)
pK
(dE/dx)
K
(kink)
K (kink) p
STAR Preliminary
<Npart> for K, p345728092358180913581004 704 253
<Npart> for 34572899221415291024 634 353 202 94-------
central
peripheral
Masashi Kaneta, LBL
Centrality dependence of Centrality dependence of T T thth and and <<rr>>
• As a function of centrality– Tth ~ 100 MeV– <r> goes up then saturated– Flow profile changed?
• Selected similar centrality region in and K,p
K
pK
p
pT [GeV/c]
]G
eV/c
)[(
2
2-2
TT
dpdy
p
nd
38 115 224 347 <Npart>
Masashi Kaneta, LBL
Bombarding Energy Bombarding Energy DependenceDependence
•From SPS to RHIC– Increasing flow–Decreasing temperature
–Longer time for cooling at RHIC?
Tth
[GeV
]<
r>
[c]
STA
R
PHE
NIX
Masashi Kaneta, LBL
SummarySummary
• The pT distributions of , K, and p are obtained as a function of centrality from RHIC-STAR at sNN=130GeV Au+Au
• The blast wave model describes the data over all of centrality
• As a function of centrality at RHIC– Tth ~ 100 MeV
– <r> goes up then saturated (~0.55c)
– Flow profile changed?
• From SPS to RHIC– Increasing flow– Decreasing temperature– Indicating longer time for cooling at RHIC?
Masashi Kaneta, LBL
Test of Flow ProfileTest of Flow Profile