# Presentation: 687870

## Pion, Kaon and Proton (Anti-proton) production in Au+Au collisions at sqrt(sNN) = 62.4GeV

- Ming Shao
*USTC/BNL*
- for the STAR Collaboration* *

- HotQuark 2004 / Taos

## Outline

-  Motivation
-  Detector & dataset
-  Particle Identification methods
-  Analysis results (spectra etc.)
-  Summary

- HotQuark 2004 / Taos

**Notes:**
Here is the outline of my talk:
First, the motivation of this work. Second, a brief introduction to the experimental detectors and the data set used in our analysis. Then I will explain the particle identification methods and followed by our analysis results base on these methods. Finally we come to the conclusion and outlook.

## Motivation

- Study the possible in-medium effect (e.g., gluon dE/dx)

-  Particle composition up to intermediate pT
-  Azimuthal anisotropy and centrality dependence of PID particles at intermediate/high pT

- Check the coalescence/recombination model

-  species dependence of v2, RCP etc.
-  particle ratio up to intermediate pT

- nucl-th/0401001

- Require hadron identification up to intermediate pT !

- HotQuark 2004 / Taos

## Experiment Detector (STAR)

**TPC-****tracking and dE/dx measurement**

**MRPC TOF (TOFr)**

**pVPD-****collision time measurement**

**TOFp**

- HotQuark 2004 / Taos

## Dataset and Cuts

**RHIC run4 (2004) 62.4 GeV Au+Au data**
**~7.2M minbias events ****	****	****	****	****	****(-30cm<z_vertex<30cm)**
**~****2.2M**** TOFr matched events**
**Main cuts applied in our analysis**
**dca(global)<3, nfitpoints>15**
**-0.5<rapidity<0**
**30<TOFr-ADC<400**
**Local TOFr hit position not exceed strip geometry bounds**

- HotQuark 2004 / Taos

## PID method ( low pT )

- PID method ( low pT )

**TPC alone PID range:   pi/k ~0.6 GeV/c,      (pi,k)/p ~1.0 GeV/c;**
**TOF “alone” PID range: pi/k ~1.6GeV/c,       (pi,k)/p ~ 3.0GeV/c**

**m****2**

**m****2**

- HotQuark 2004 / Taos

## PID method ( intermediate pT )

- PID method ( intermediate pT )

- p

- K

**yield_******** = 2*yield_********(n************>0)**, if the n is a normal Gaussian distribution

**Combine TPC (n************,K,p****) and TOF (m****2****) information, the PID range could be greatly extended **

- 

- HotQuark 2004 / Taos

## Correction of n

- Correction of n

| pT range
(GeV/c) | n Gaussian parameters |  |
| --- | --- | --- |
|  | mean | sigma |
| 0.9-1.0 | -0.194 | 0.981 |
| 1.0-1.2 | -0.200 | 0.970 |
| 1.2-1.4 | -0.185 | 0.943 |
| 1.4-1.6 | -0.186 | 0.949 |
| 1.6-1.8 | -0.209 | 0.915 |
| 1.8-2.0 | -0.256 | 0.916 |
| 2.0-2.5 | -0.194 | 0.962 |

- Choose constant n Gaussian parameters of **mean=-0.2** and **sigma=0.95**, so 		          **yield_******** =**** ****2.40*****yield_********(n************>0)**;
- Similarly, for p(pbar) we have     **mean=-0.2** and **sigma=1.0**, and 	        **yield_p = ****1.73*****yield_p(n********p****<0)**

- HotQuark 2004 / Taos

## , K and p(pbar) yield (minbias)

- , K and p(pbar) yield (minbias)

- PRELIMINARY

- PRELIMINARY

- Minbias means (0-80%)
- Efficiency corrected, but no background correction
- Statistic errors only

- HotQuark 2004 / Taos

##  yield 

-  yield

- PRELIMINARY

- PRELIMINARY

| Centrality | Refmult cut (>=) |
| --- | --- |
| 0-10% | 313 |
| 10-20% | 222 |
| 20-40% | 102 |
| 40-80% | 9 |

- HotQuark 2004 / Taos

## K yield 

- K yield

- PRELIMINARY

- PRELIMINARY

- HotQuark 2004 / Taos

## p/pbar yield 

- p/pbar yield

- PRELIMINARY

- PRELIMINARY

- HotQuark 2004 / Taos

## Summary

- By combining TPC and TOF information, we can measure ,K and p spectra in intermediate pT range
- Preliminary spectra of ,K and p up to pT=5GeV/c are acquired in 62GeV Au+Au collisions

- HotQuark 2004 / Taos

## Thank you !

- HotQuark 2004 / Taos

## anti-hadron / hadron ratio

- PRELIMINARY

******-****/ ********+****: 1.017****±****0.002**
**K****-****/K****+****: 0.835****±****0.006**
**pbar/p: 0.458****±****0.005**

- Significant baryon number excess

- HotQuark 2004 / Taos