Pawan Kumar Netrakanti,VECC, Kolkata (For STAR Collaboration)

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

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Identified hadron spectra at large transverse momentum in p+p and d+Au collisions at

sNN=200 GeV

Pawan Kumar Netrakanti,VECC, Kolkata (For STAR Collaboration)


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Motivation Method of analysis Results from p+p collisions Results from d+Au collisions Summary

Outline

STAR preliminarySTAR preliminary



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Motivation

Understanding Nuclear effects in d+Au collisions

Test predictions (certain aspects) of pQCD

High pT PID in TPC


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Method of analysis

Intrinsic timing resolution: 85 ps Coverage : -1.0 < < 0.0 and in low pT particle identification ( < 2.5 GeV/c) in this study

Hadron identification: STAR Collaboration, nucl-ex/0309012

High pT : Extend particle identification in TPC by exploiting the relativistic rise in ionization energy loss.

Log10(p)

Log1

0(dE

/dx)

Momentum: GeV/cdE/dx of K,p) separation: 2

10~3 p

High pT Time Projection Chamber (TPC)

Low pT Time of Flight (TOF)

Coverage: |andsymmetric


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Transverse Momentum SpectraSTAR preliminarySTAR preliminary

Power-law : ( A/(1 + pT/p0)n)Levy : (B/(1+(mT-m0)/nT)n)

Power-law function ~ pQCD inspiredLevy ~ exponential + power-law

Power law type behavior for p+p and d+Au collisions at high pT


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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


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p+p collisions and phenomenological model

Phenomenological EPOS Model are consistent with pion data, even at low pT.Phenomenological EPOS Model are consistent with p + pbar data, even at low pT.Interesting to observe that two different models (pQCD and EPOS) do a reasonable job in p+p collisionsK. Werner, F. Liu and T. Pierog, hep-

ph/0506232


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Scaling in particle production

e+ and e- does not have a parton distribution function.There will be a (sNN )2 multiplied to cross-section in e+e- collisions. For p+p collisions n ~ 6.5 for , p

(pbar)


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d+Au collisions and models•NLO pQCD calculations with KKP and AKK FF and EPOS are consistent with pion data at high pT (> 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


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Nuclear Modification Factor : d+Au collisions

RdAu for > 1, Cronin effect Absence of high pT suppression in particle production RdAu (p + pbar) > RdAu () 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



evt 2AB AB T

AB 2AB pp T

1 N d N /dydpR

T d /dydp

Phys. Rev. Lett. 91 (2003) 072304


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Particle Ratios – p+p collisions

-/+ ~ 1 and pbar/p ~ 0.8 PYTHIA predicts a more prominent pT dependence p/+ and pbar/ - increases with pT ~ 2 GeV/c and then decreases to ~ 0.2 p/+ agrees with lower energy results. pbar/ - shows a distinct energy dependence


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Particle Ratios – d+Au collisions

STAR preliminarySTAR preliminary -/+ ~ 1- independent of pT

pbar/p decreases with pT

p/+ and pbar/- increases with pT up to 2 GeV/c and then decreases.


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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 xT 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


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The STARSTAR CollaborationU.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

STARSTAR


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Scaling of particle production

mT scaling observed for1 < mT < 2 GeV/c2


At high pT : no scalingMass effect

Or baryon-meson effect

Documents

Pawan Kumar Netrakanti,VECC, Kolkata (For STAR Collaboration)