# Presentation: 504011

## Slide 1

## Space-time Evolution in Relativistic Heavy Ion Collisions

**Hadronization **
**  ****(Freeze-out)**
**           ****+**
**   ****Expansion**

**Pre-equilibrium**

**Thermalization**

**QGP phase**

**Mixed phase**

**Hadrons reflect**** ****the bulk property of created system and its evolution!**

## Physics of Identified Hadron

** ****Hydro-dynamical collective expansion velocity**** (********. **
** ****Thermal freeze-out temperature**** (*****T*****th****).**
** ****Chemical freeze-out temperature and **
**   ****chemical potential**** (*****T*****ch****, ********B****)**
**                                                                                         **
** ****Jet quenching effect at high p****T**** by parton **
**   ****energy loss in medium (dE/dx).**
** ****Space-time evolution of the system **

**p****T**** spectra**

**dN/dy**

**High p****T**** spectra**

_**Shed light on QGP formation at RHIC**_

**HBT correlation**

## Outline

**Experimental setup and PID by TOF.**
**Identified charged hadron spectra.**
**Spectra shape**
**Inverse slope parameter vs. centrality**
**Particle ratios**
**HBT ********+********+****, ********-********-**** correlations.**

_***In this presentation, we present the recent preliminary results in***_
**Au+Au collisions,          = 130 GeV @ mid-rapidity |********| < 0.35,**
**Measured at RHIC-PHENIX.**

## PHENIX Detector Setup

** ****Beam-Beam Counter   ****	****	****(BBC) **
***     ******z vertex, start timing for TOF***
** ****Time-of-Flight (TOF)**
**    *****stop timing measurement***
* ***Drift Chamber (DC)**
***   ******momentum, flight path length***
** ****Pad Chamber 1 (PC1)**
**   *****additional track z information to Dch***

**In this analysis, we use**

## Reality of PHENIX

**EAST ARM**

**TOF WALL**

**CENTRAL MAGNET**
** ****+ MUON ARM**

## Particle Identification by TOF

**TOF – TOF ****expected **** [ns]**

** ****Demonstrated clear PID by TOF**
** ****Time-of-Flight resolution**
******TOF**** ~ 110-120 ps **(@ 3/27/01)
** ****Flight path length : ~ 5m**
** ****K/******** separation : < 2 GeV/c**
** ****p/K separation : < 4 GeV/c**

## PID Cut Criteria

***Proton***

**K****+**

**********+**

***m*****2**** [(GeV/c****2****)****2****]**

- All momentum

**(****a.u.)**

-  **w/o PID cut**

-  PID by *m*2 vs. momentum space
-  |*m*2measured - *m*20| < 2.5 m2
-  Momentum cutoff

## Centrality Classes

_**Dch raw multiplicity distributions**_

| Centrality | Participants |
| --- | --- |
| 0-5% | 347  15% |
| 5-15% | 271  15% |
| 15-30% | 178  15% |
| 30-60% | 76  15% |
| 60-80% | 19  60% |
| 80-92% | 5  60% |

** ****Used correlation between BBC charge**
**   ****and ZDC energy to define centrality.**
** ****Extracted *****N*****part**** based on Glauber model.**

## Results : Minimum bias pT spectra 

| particle | pT range |
| --- | --- |
| p | 0.3  -  1.8 GeV/c |
| K | 0.5  - 1.6 GeV/c |
| proton | 0.5  -  3.0 GeV/c |
| pbar | 0.8  -  3.0 GeV/c |

** ****pions yield ~ proton/pbar yield **
**   ****@ p****T****~ 2 GeV/c.**
** ****How m****T**** spectra look like?**
**	******** ****next slide**

## Minimum bias mT spectra

** ****In 0.2 < m****t**** – m****0**** < 1.2 [GeV/c****2****], spectra **
**   ****for all species scaled by single exp.**
**   ****function.**
** ****Similar inverse slope for ******** and K.**
** *****T*****proton**** > *****T********* **

** ************     ****~ 205 ******** ****5  (stat.)  ******** ****15 (sys.)  MeV**
** ****K ********     ****~ 215 ******** 5  (stat.) ******** 20 (sys.)   MeV**
** ****p,     ~ 320 ******** 10 (stat.) ******** 20 (sys.)  MeV**

**Fitting results by single exp. function**

## Centrality Dependence of mT Spectra for  

** ****Single exponential scaling at 0.2 -1.0 GeV in m****t****-m****0 ****(soft region).**
**   ****(power low shape in most peripheral event ?)**
** *****T********* (central 0-5%) ~ 210 MeV ********5 (stat.) ********15 (sys.)  MeV.**
** ****Applied same parameterization for kaons and (anti-) protons.**

## Centrality dependence of mT slope

** ****Weak centrality dependence **
**   ****for *****T********* and *****T*****K****. **
** ****Gradual rise of *****T*****proton**** and *****T*****pbar**** **
**   ****from peripheral to mid-central **
**   ****collisions.**
** *****T********* ******** *****T***** ****K**** < *****T*****proton**

## Mass Dependence of T

**Intuitive explanation of mass **
**dependence of *****T***

** ********t**** : Transverse expansion velocity**

** **_**Good agreement with Hydro+UrQMD (cascade model).**_

## Comparison with CERN Energy

**PHENIX Preliminary**

** ****The slopes of pions and protons at RHIC are **
**  ****higher than that of Pb+Pb collisions at SPS.**
_** **__**Large transverse flow @ RHIC than SPS?**_

- SPS data : NA44
- (most central)

- NOTE: fitted at
-  <1.0 GeV/c2 in mt-m0

## K+/K- and pbar/p ratio vs. centrality

**No clear dependence as a function of centrality (N****part****)  in both K****+****/K****-**** and pbar/p ratios.**
**K+/K- @5% central = 1.29±0.07(stat) ±0.19(sys.)**
**pbar/p****	****            = 0.54±0.01(stat.)±0.08(sys.)**

-  Systematic errors ~15%

**K****+****/K****-**

** ****pbar/p**

## Beam Energy Dependence of ratios

**C+C**

**Ni+Ni**

**KaoS**

**E866**
**Au+Au**

**Si+Au**

- S+S

**PHENIX ****preliminary**

**NA44**
**Pb+Pb**

**PHENIX ****preliminary**

**E866**
**Au+Au**

**NA44**
**Pb+Pb**

-  pbar/p

**K****+****/K****-**

** ****pbar/p**

**  ****SIS     AGS          SPS               RHIC**

- K+/K-

- 1.0

_**Both ratios are closing to 1.0 from AGS, SPS to RHIC energy.**_

## RHIC data point in B-T plane

_**Statistical thermal model**_

- hep-ph/0002267  F.Becattini et al.

_**Baryon chemical potential ~ 50MeV, not baryon free(**__****__**B**__**=0).**_** **** **

**PHENIX  preliminary**

## HBT correlations

**Extraction of source size “R”**
**using quantum interferometry**

**C****2**

**Assume Gaussian r****eff**
** ****with width “R”**

** ****Correlation function C****2**** **

## 3D HBT measurement in PHENIX

**~ ****q****Tside**

**~ ****q****Tout**

**q****long**

** ****Full analytic coulomb corrections.**
** ****Taking account two track separations.**
** ****Minimum-bias data sample.**

_**Bertsch-Pratt parameterization**_

## Bertsch-Pratt Fit Results (TOF PID)

**R****long****  = 6.7 ******** 0.9**
**R****Tside**** = 5.8 ******** 1.5**
**R****Tout **** = 5.49 ******** 0.54**
******       ****= 0.493 ******** 0.061**

**R****long****  = 4.0 ******** 1.2**
**R****Tside**** = 7.9 ******** 1.1**
**R****Tout****  = 6.23 ******** ****0.54**
******= 0.493 ******** ****0.050**

-  ****+****+

-  ****-****-

## Beam energy dependence of R

**Beam energy dependence of R**

**No indication of large volume **
**No big jump from SPS to RHIC**
**       **
**      ****Due to ....**
** ****High expansion velocities? **
**      ****( i.e. *****x-p***** correlation)**
** ****Resonance contributions?**

**AGS     SPS      RHIC**

## Conclusions from Year-1 data

- Single particle spectra for , K , protons and anti-protons in each centrality class and 2 HBT correlations are studied.
- Weak centrality dependence of slopes for *T* and *T*K.
- Gradual rise of *T*proton and *T*pbar from peripheral to mid-central collisions.
*T*  *T* K < *T*proton at all centrality classes.
- The slope of pions and protons at RHIC are higher than that of Pb+Pb collisions at SPS (indicative of large expansion velocity @ RHIC).
- Weak centrality dependence in both K+/K- (~1.29) and pbar/p (~0.54).
- Baryon chemical potential ~ 50MeV (thermal model), not baryon free(B=0).
- No indication of large source size in 2 HBT measurement.

**Start next data taking from May 2001!**
** ******** ****~1000 data will come soon, and more physics**

## See also

**28****aSG7 : Measurement of hadron spectra at RHIC-PHENIX experiment**
**	****	****       *****M. Suzuki (Univ. of Tsukuba)***
**28aSG8 : Study of charged particle ratios at RHIC-PHENIX experiment**
**	****	****       *****A. Kiyomichi (Univ. of Tsukuba)***