1. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 1 Identified hadron spectra at large transverse momentum in p + p and d +Au collisions at  s NN = 200 GeV Pawan Kumar Netrakanti,VECC, Kolkata (For STAR Collaboration)

2. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 2 Motivation Method of analysis Results from p+p collisions Results from d+Au collisions Summary Outline STAR preliminary

3. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 3 Motivation Understanding Nuclear effects in d+Au collisions Test predictions (certain aspects) of pQCD High p T PID in TPC

4. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 4 Method of analysis Intrinsic timing resolution: 85 ps Coverage : -1.0 <  < 0.0 and   in   low p T particle identification ( < 2.5 GeV/c) in this study Hadron identification: STAR Collaboration, nucl-ex/0309012 High p T : Extend particle identification in TPC by exploiting the relativistic rise in ionization energy loss. Log10(p) Log10(dE/dx) Momentum: GeV/c dE/dx of  K,p) separation: 2  High p T  Time Projection Chamber (TPC) Low p T  Time of Flight (TOF) Coverage: |  and  symmetric

5. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 5 Transverse Momentum Spectra STAR preliminary Power-law : ( A/(1 + p T /p 0 ) n ) Levy : (B/(1+(m T -m 0 )/nT) n ) Power-law function ~ pQCD inspired Levy ~ exponential + power-law Power law type behavior for p+p and d+Au collisions at high p T

6. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 6 Comparison to NLO pQCD NLO pQCD with AKK FF relatively better than KKP for the p+pbar data AKK differ from KKP, in the way the light flavor FF are obtained NLO pQCD with Kretzer FF inconsistent with data NLO pQCD with KKP FF inconsistent with the p+pbar data Kretzer differ from KKP, in the gluon to  fragmentation

7. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 7 p+p collisions and phenomenological model Phenomenological EPOS Model are consistent with pion data, even at low p T. Phenomenological EPOS Model are consistent with p + pbar data, even at low p T. Interesting to observe that two different models (pQCD and EPOS) do a reasonable job in p+p collisions K. Werner, F. Liu and T. Pierog, hep-ph/0506232

8. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 8 Scaling in particle production e + and e - does not have a parton distribution function. There will be a (  s NN ) 2 multiplied to cross-section in e + e - collisions. For p+p collisions n ~ 6.5 for , p (pbar)

9. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 9 d +Au collisions and models NLO pQCD calculations with KKP and AKK FF and EPOS are consistent with pion data at high p T (> 4 GeV/c) pQCD calculations with Kretzer FF under predicts pion data NLO pQCD calculations with only AKK fragmentation function consistent with the p+pbar data Parton distribution functions : L. Frankfurt, et al., Phys. Rev. D 71 (2005) 054001 D. De Florian and R. Sassot, PRD 69 (2004) 074028 STAR Preliminary

10. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 10 Nuclear Modification Factor : d +Au collisions  R dAu for  > 1, Cronin effect  Absence of high p T suppression in particle production  R dAu (p + pbar) > R dAu (  ) Similar dependence has been observed at lower energies. Phys. Rev D 19 (1979) 764 Qualitative agreement with recombination model for dAu collisions. Phys.Rev.Lett.93 (2004) 082302 STAR preliminary Phys. Rev. Lett. 91 (2003) 072304

11. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 11 Particle Ratios – p+p collisions   - /  + ~ 1 and pbar/p ~ 0.8  PYTHIA predicts a more prominent p T dependence  p/  + and pbar/  - increases with p T ~ 2 GeV/c and then decreases to ~ 0.2  p/  + agrees with lower energy results.  pbar/  - shows a distinct energy dependence

12. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 12 Particle Ratios – d +Au collisions STAR preliminary   - /  + ~ 1- independent of p T  pbar/p decreases with p T  p/  + and pbar/  - increases with p T up to 2 GeV/c and then decreases.

13. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 13 Highlight and Summary NLO pQCD describes the p+pbar spectrum for the first time in p+p collisions These results show the importance of the significant improvement of FF for baryons from the light-flavor separated measurements in e + e - collisions (OPAL) The observed x T scaling of ,p(pbar) at high pT also show dominance of hard processes related to PDF and FF Provide solid reference for effects of jet quenching and recombination in Nucleus-Nucleus collisions Details of these results can be found at: arXive: nucl-ex/0601033

14. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 14 STAR The STAR Collaboration U.S. Labs: Argonne, Lawrence Berkeley, and Brookhaven National Labs U.S. Universities: UC Berkeley, UC Davis, UCLA, Caltech, Carnegie Mellon, Creighton, 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, Kolkata Netherlands: NIKHEF/Utrecht Poland: Warsaw University of Technology Russia: MEPHI – Moscow, LPP/LHE JINR – Dubna, IHEP – Protvino South Korea: Pusan National University Switzerland: University of Bern STAR

15. Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 2006 15 Scaling of particle production m T scaling observed for 1 < m T < 2 GeV/c 2 STAR preliminary At high p T : no scaling Mass effect Or baryon-meson effect