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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.

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Presentation on theme: "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."— Presentation transcript:

1 Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 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 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 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 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/ 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 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 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 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/

8 Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 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 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) D. De Florian and R. Sassot, PRD 69 (2004) STAR Preliminary

10 Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 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) STAR preliminary Phys. Rev. Lett. 91 (2003)

11 Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 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 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 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/

14 Pawan Kumar Netrakanti QGP-MEET 2006, VECC, February 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 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


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