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

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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