# Presentation: 625239

## Slide 1

## Physics of Soft Hadron

** ****Hydro-dynamical collective expansion velocity**** (********  **
**  ****and thermal freeze-out temperature**** (*****T*****th****).**
** ****Chemical freeze-out temperature and **
**   ****chemical potential**** (*****T*****ch****, ********B****, ********S****)**
**                                                                                         **
** ****Space-time evolution of the system **

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

**dN/dy, ratio**

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

**HBT correlation**

**K****T**** dependence of **
**HBT correlation radius**

**Soft hadrons contain the bulk property of created system **
**and its dynamical evolution!**

## Outline

**Experimental setup and hadron PID by TOF.**
**Identified charged hadron spectra.**
**Spectra shape**
**Inverse slope, <p****T****> vs. centrality**
**Particle ratios (pbar/p, K****+****/K****-****)**
**HBT ********+********+****, ********-********-**** correlations**** ****(TOF, EMC analysis).**

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

** ****Based on the post QM01 analysis (to be published in the QM proceedings).**
** ****Due to the time restriction****, ****I will skip the results of elliptic flow analysis.**

## 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***
***                               ******+***
*** *****PbSc EMCal (EMC)**
***  ******as TOF detector for HBT analysis******      ******                    ***

**In this presentation, 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 : < 1.6 GeV/c**
** ****p/K separation : < 3.5 GeV/c**

## PID Cut Criteria

-  PID by *m*2 vs. momentum space
-  |*m*2measured - *m*20| < 2 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% |
| 60-92% | 12  60% |

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

## Corrections for raw pT spectra

-  Correction factor based on the single particle MC simulation for each particle species.
** **Including geometrical acceptance and decay effect.
** **Taking into account track reconstruction efficiency in each centrality
-    bin by using the embedding method.

_**Correction functions**__ _

- pT [GeV/c]

_**Track reconstruction efficiency**__ _

**Central                                                  Peripheral**

- * Arrows indicate the upper limit of pt region

## Results : Minimum bias pT spectra 

** ****pions yield ~ proton and pbar yield  @ p****T****~ 2 GeV/c, **
** ****Indicated that p/pbar is dominant at high p****T**** region.**

## Centrality Dependence of pT Spectra for and anti-proton 

** ****Power law shape is prominent in peripheral event for pions.**
**  ****<p****T****> are extracted by fitting the each spectra in whole p****T**** range.**
**	********      ****: power**** ****law function,**
**              ****p/K,  : single exponential function.**

## <pT> vs. centrality

**Interpolation to sqrt(s)=130 GeV**
**From p     collisions**

** ****The heavier mass, the larger <p****T****>. **
** ****Continuous rise for proton, anti-proton (K), rather flat distribution for ********.**

## Minimum bias mT spectra

** **

** ****For protons and kaons, single exponential shape up to 1.0 GeV/c****2****.**
** ****For pions, power law like behavior.  **

## Mass dependence of mT slope

** ****Clear mass dependence of *****T*****.**
** *****T********* < *****T***** ****K**** < *****T*****proton ****, especially for most central collisions. **

- Fitted to exponential in mT – m0

** ************   ****= 180  ******** ****11  MeV      ,  ********-  **** =  179  ********  13 MeV **
** ****K****+   ****=  237 ******** 17  MeV      ,  K****-  **** =  258  ******** 37 MeV**
** ****p    =  302 ******** 22 MeV       ,        =  347  ******** 36 MeV**

**Inverse slope**
**@ 5% ****central**

| particle | Fitting range in pT  |
| --- | --- |
|  | 0.3  -  0.9 GeV/c |
| K | 0.55  - 1.6 GeV/c |
| proton | 0.55  -  1.6 GeV/c |

## Centrality Dependence of T

** ****Continuous rise of *****T*****proton****, *****T*****pbar**** as a function of N****part****, while rather flat for T********, T****K**** .**
** *****T********* < *****T***** ****K**** < *****T*****proton ****@ most central collision consistent with expansion picture.**

**Simultaneous fitting by **
**hydrodynamic model **
** ****to the data @ 5% central.**
**T****fo****~ 125 - 83 MeV ******** 8% (sys)**
******t****  ~  0.6 - 0.8 ******** 5% (sys)**
**(calculated by J. B Burward-Hoy, SUNY)**

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

**K****+****/K****-**** and pbar/p ratios vs. centrality**

**No clear dependence as a function of N****part**** in both K****+****/K****-**** and pbar/p ratios.**
**K****+****/K****-****   (Min. Bias)  ****	****= 1.08±0.03(stat) ±0.22(sys.)**
**pbar/p (Min. Bias)  ****	****= 0.64±0.01(stat.)±0.07(sys.)**

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

** ****pbar/p**

## K+/K- and pbar/p ratios vs. pT

**Within the systematic errors, No clear p****T**** dependence in both K****+****/K****-**** and pbar/p ratios.**

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

** ****pbar/p**

- Minimum Bias

- Minimum Bias

## Beam Energy Dependence of ratios

** ****Both ratios are closing to 1.0 from AGS, SPS to RHIC energy.**
** ****Baryon chemical potential ~ 40MeV, not baryon free (********B****!=0).**

_**Statistical thermal model**_

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

******B**** (MeV)**

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

## 3D HBT measurement in PHENIX

**3D HBT measurement in PHENIX**

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

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

**q****long**

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

_**Bertsch-Pratt parameterization**_

## Bertsch-Pratt Fit Results I (TOF PID)

**R****long****  = 6.7 ******** 0.9 fm**
**R****Tside**** = 5.8 ******** 1.5 fm**
**R****Tout **** = 5.5 ******** 0.5 fm**
******       ****= 0.49 ******** 0.06**

**R****long****  = 4.0 ******** 1.2 fm**
**R****Tside**** = 7.9 ******** 1.1 fm**
**R****Tout****  = 6.2 ******** ****0.5 fm**
******= 0.49 ******** ****0.05**

-  ****+****+

-  ****-****-

- * Correlation functions have been
-    fully Coulomb corrected in TOF, EMC analysis

## Bertsch-Pratt Fit Results II (EMC PID)

-  ****+****+

-  ****-****-

**R****long****  = 5.9 ******** 0.4 fm**
**R****Tside**** = 5.1 ******** 0.6 fm**
**R****Tout **** = 4.4 ******** 0.2 fm**
******       ****= 0.27 ******** 0.02**

**R****long****  = 5.9 ******** 0.4 fm**
**R****Tside**** = 5.0 ******** 0.6 fm**
**R****Tout****  = 5.1 ******** 0.2 fm**
******= 0.30 ******** 0.02**

-  Note 1 : EMC radii are consistent with TOF results within error bars.
-  Note 2 :  are different, but it’s understood in terms of different S/B between the two
-                  analysis.

## Beam energy dependence of R

**Beam energy dependence of R**

**Moderately larger source size compared with SPS. **
**No big jump from SPS to RHIC**

**AGS     SPS      RHIC**

** ****R****L****, R****TS ****; increase**
** ****R****TO****      ; flat **

**as a function of beam energy**

## kT dependence of HBT radii

**Related to degree of collective motion**

- * From EMC analysis

** ****Consistent with expanding**
**  ****source picture.**

## 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 and <p****T****> for pions****. **
**For protons and anti-protons, continuous rise of**** ****slopes and <p****T****>**** ****from peripheral to central collisions are observed.**
***T********* < *****T***** ****K**** < *****T*****proton**** ****at all centrality classes, which is consistent with expanding source picture @ RHIC energy.**
**No clear centrality and p****T**** dependence in both K****+****/K****-**** (~1.08) and pbar/p (~0.64) ratios.**
**Baryon chemical potential ~ 40MeV (thermal model); indicative of not baryon free(********B****=0) system in Au+Au at           = 130 GeV.**
**In 2******** HBT measurements,  moderately larger source radii are observed.**
**k****T**** dependence of radii suggests the larger collective motion, which is consistent with the observation of single particle analysis.**