# Presentation: 923311

## Radial Flow Study from Identified Hadron Spectra in Au+Au collisions at                   200GeV

**Akio Kiyomichi **(RIKEN)
- for the PHENIX Collaboration
**E-mail: kiyo@riken.go.jp**
**http://www.phenix.bnl.gov/~kiyo/**

**Decay**

- Inclusive ****
- distribution

******2**** ****test**

**Hydro-dynamical model with resonance**

- Daughter ****
- distribution

**Procedure:**
- Generate resonances with *p**T* distribution determined by each combinations of **T****fo****, **********T**.
- Decay them and obtain pT spectra of ,K,p.
- Particle abundance calculated with chemical parameters : **T****ch**** = 177MeV, ********B**** = 29MeV**
**Ref:**_**P.Braun-Munzinger et al,PLB518(2001)41.**_
- Merge and create inclusive pT spectra.  ******2**** test**

**Centrality dependence of *****T*****fo**** and <**********T****>**

**Contour plot of *****T*****fo**** vs. <**********T****> for each centrality**

- Create inclusive *p**T* spectra
- for each particles, each (Tfo , T)

**Results**

**Blast-wave model parameterization**

*Expansion parameters:*
*    **normalization**** A***
*    **freeze-out temperature**** ******T*****fo**
***    ****surface velocity**** ************T***

- definite integral from 0 to R
- particle density distribution
- 	***f***(r) ~ const

**Ref:**_**Sollfrank,Schnedermann,Heinz,PRC48(1993)2462.**_

**I****0**** , K****1**: modified Bessel function

- Use  _**linear flow rapidity profile**_ and _**constant particle density**_

- linear profile **n = 1**: *********r*** = *********T*** • r/R
- average velocity: ***<************T****** >*** = 2/3 *********T***
_**S.Esumi,S.Chapman,H.van Hecke,and N.Xu,**_
_**Phys.Rev.C 55, R2163 (1997)**__ _

**Hadron measurement.**
-  DCH+PC1+TOF+BBC
-   = /8, -0.35 <  < 0.35
**Particle ID by TOF**
-  **** : 0.2< *p**T* < 3.0 GeV/c
-  **K** : 0.4< *p**T* < 2.0 GeV/c
-  **p** : 0.6< *p**T* < 4.5 GeV/c

**PHENIX Detectors for Charged Hadron PID**

**Mean *****p******T***** vs. centrality**

**PID *****p******T***** Spectra**

- Increase from peripheral to mid-central, and then saturate from mid-central to central for all particle species.
- Observed clear mass dependence.
**Indicative radial expansion. ****(consistent with hydro picture)**

**Central**
- Low *p**T* slopes increase with particle mass.
- Proton and anti-proton yields equal the pion yield at high *p**T*.
**Peripheral**
- Mass dependence is less pronounces.
- Similar to pp.

_**PHENIX: PRC accepted,nucl-ex/0307022**_

**Radial Flow Study from Identified Hadron Spectra ****in Au+Au collisions at                   200GeV**

**Resonance:**
-   , K, p, anti-p
-  
-  K*, K*0, anti-K*0, **
-  , , 0,anti-

**Fitting region:**
- Minimize contribution from hard process.: **(m****T ****-**** m****0****) < 1GeV/c****2**
-  ******: < 1.2GeV/c, K : < 1.4GeV/c, p : < 1.7GeV/c**
- Exclude large resonance for pion at very low *p**T* .  ******: *****p******T***** > 0.5GeV/c**

**Experimental data: Identified charged hadron p****T**** spectra**
**in Au+Au collisions at ********s****NN**** = 200 GeV from PHENIX**

- Simultaneous fit in meth.
- Tfo : 60~240MeV, 4MeV each
-  *********T***: 0.0~0.9c, 0.02c each

_**N**__**part**__** dependence of expansion is observed.**_
- @central: **saturate**
- @peripheral: 	**N****part ******** 0 :: *****T*****fo**** increase, *****<************T******>***** ******** 0**

**Chemical parameter:**
-  **T**ch~177MeV,****b ~29MeV

**Study of Hydro-dynamical Collective Expansion Picture**
_**Identified charged hadron spectra and yield**_
- Spectra vs. centrality
- Mean *p**T* vs. centrality
_**Hydro-dynamical model fit**_
- Radial flow velocity ******T and thermal freeze-out temperature ***T*****fo**
- Hydro-dynamical model with resonance decay effect.

_**Hydro-dynamical model fit to the spectra with resonance decay effect**_

- For the most central:
*Freeze-out temperature*** *****T*****fo**** = 100MeV**
*Average flow velocity**** <************T******>***** = 0.5 ****(***Surface flow velocity*** ***********T***** = 0.76, ****< ***********T***** > = 2/3 ***********T*****)**

- Akio Kiyomichi [RIKEN]

- Quark Matter 2004, Orkland January 11-17