# Presentation: 748819

## Bedanga MohantyLawrence Berkeley National LaboratoryandVariable Energy Cyclotron Centre  (For STAR Collaboration)

- _Outline_

- Motivation
- Measurement (,p,pbar)
- Energy dependence ( √sNN = 62.4 and 200 GeV)
- System size dependence (Cu+Cu and Au+Au)
- Summary

***Quark Matter 2006, Shanghai***

- Bedanga MohantyLawrence Berkeley National LaboratoryandVariable Energy Cyclotron Centre  (For STAR Collaboration)

## Motivation (I)

- Comparison to models constrains
-      Initial gluon density (dNg/dY)
-      Life time (
- Study vs. Energy, pT, Npart
-   Radiative or Collisional Eloss?

- Jet quenching

- Nuclear Modification Factor

## Motivation (II)

- Coalescence ** **

- Specific Energy dependence
-  p/ (62.4 GeV) > p/ (200 GeV)
- Time for quantitative comparison
-  Data (Energy, pT, Npart) & Models (Baryon junction and Recombination ?)

- p/ and pbar/

- V. Greco, C.M. Ko and I. Vitev,
- PRC 71 (2005) 041901

## Motivation (III)

- Color charge dependence of Eloss

- NMF and pbar/-

- X-N. Wang, PRC 71(2005) 014903

**x****T**** = 2p****T****/√s****NN**

- Eloss(g)/Eloss(q) ~ 9/4
- For same pT relative
- contribution of quark and gluon jets differ at 62.4 and 200 GeV

**R****AA**

**p****T**

## Measurements

**+**

- Au+Au 200 GeV

- TOF

**(-0.5 < |********| < 0.5)**

**(-1.0 < |********| < 0.0)**

**(STAR : PRL **97, 152301 (2006)**)**

**NIM A 4**99, 659 (2003)

**NIM A 508**, 181 (2003)

## Energy dependence : spectra & yields

- Integrated yields

- Proton yields : Interplay of baryon production
- and baryon transport at mid rapidity

**peripheral**

**central**

## Energy dependence : Anti-particle-to-particle ratios

## Energy and species dependence of NMF

## Energy dependence and Model comparison : NMF

- Steeper initial jet spectra ?
- Or Color charge dependence ?
- At same pT : ~ 3 difference in xT

- Suggests of radiative Eloss dominant

- Plasma formation time < 3.6 fm/c
- V.S. Pantuev, hep-ph/0604268

- pp 62 GeV : D. d’Enterria,
- J. Phys. G 31 (2005) S491

## Energy dependence and Model comparison : NMF

- dNg/dy (62.4) <800
- dNg/dy (200) > 800
-  ~> system size
- Collisional Eloss reasonable !

## Centrality and √sNN dependence : Baryon/meson

- Strong centrality dependence

## Model comparison and scaling of Baryon/meson

- /K0s 200 GeV : nucl-ex/0601042

## Energy dependence in Cu+Cu system 

- Similar energy dependence in
- Cu+Cu collisions as seen in Au+Au
- collisions

## System size dependence 

- For collisions with similar
- Nbin and Npart the high pT results  in
- Cu+Cu and Au+Au collisions
- are similar

- **-**** + ****+**

## Summary 

- Intermediate pT
-   (2 - 6 GeV/c)

- p(pbar)/ : Qualitatively consistent with coalescence predictions
-                       but strong Quantitative disagreement
-  Similar shape of  p/pbar/ and/K0s ratios at 62.4 and 200 GeV observed

- Measurements

- +,-,p,pbar spectra measured in STAR upto pT = 12 GeV/c in
- Au+Au and Cu+Cu collisions at 62.4 and 200 GeV

- System size

- For same Nbin, Cu+Cu and Au+Au results at high pT are similar

## STAR Collaboration

**U.S. Labs:**
- 	Argonne,   Lawrence Berkeley,  and Brookhaven National Labs
**U.S. Universities:**
- 	UC Berkeley, UC Davis,  UCLA,  Caltech**,** Carnegie Mellon, Creighton,  Illinois-Chicago, Indiana, Kent State, MIT, MSU,  CCNY, Ohio State, Penn State,  Purdue,  Rice, Texas A&M, UT Austin, Washington, Wayne State, Valparaiso, Yale
**Brazil:****	**
- 	Universidade de Sao Paolo
**China:****	****    **
- 	IHEP - Beijing, IPP - Wuhan, USTC,
- 	Tsinghua, SINAP, IMP Lanzhou
**Croatia:****	****    **
- 	 Zagreb University
**Czech Republic:****	****    **
- 	 Nuclear Physics Institute
**England:**
- 	University of Birmingham

**France:****     **
- 	Institut de Recherches Subatomiques Strasbourg, SUBATECH - Nantes
**Germany:****  **
- 	Max Planck Institute – Munich University of Frankfurt
**India:**
**	**Bhubaneswar, Jammu, IIT-Mumbai, Panjab, Rajasthan, VECC
**Korea:**
- 	Pusan Nat’l University
**Netherlands:**
- 	NIKHEF
**Poland:**
- 	Warsaw University of Technology
**Russia:****  **
- 	MEPHI – Moscow,  LPP/LHE JINR – Dubna,  IHEP – Protvino

***Thanks!***** **

## Back up slide (B/M ratio)

## Back up slide (STAR-PHENIX)

- p+p collisions

## Back up slide (NMF)

## Back up slide (NMF)

## Back up slide (B/M ratio)