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Particle Identification at high p T in p+p collisions at 200 GeV @ RHIC-STAR

Particle Identification at high p T in p+p collisions at 200 GeV @ RHIC-STAR. Yichun Xu ( 许依春 ) Center for Particle Physics and Technology University of Science and Technology of China. Outline. Motivation Extend the identified hadron spectra to higher p T range.

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Particle Identification at high p T in p+p collisions at 200 GeV @ RHIC-STAR

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  1. Particle Identification at high pT in p+p collisions at 200 GeV @ RHIC-STAR Yichun Xu (许依春) Center for Particle Physics and Technology University of Science and Technology of China Yichun Xu@Central China Normal University,Wuhan

  2. Outline • Motivation • Extend the identified hadron spectra to higher pT range. • Good constraints to pQCD calculations. • Baseline for study of nuclear modification factor (RAA) in Heavy Ion Collisions. • Data analysis • Identify charged p, K, p(p) by ionization energy loss (dE/dx) • Reconstruct K0Sp++p-using EMC as a hadron trigger • Summary Yichun Xu@Central China Normal University,Wuhan

  3. Good constraints to pQCD calculation Ng(i)/ (Ng(i) + Nq(i)); i = , K, p… Large gluon contribution (~90%) to produced baryons @ high pT; Substantial quark contribution (~40%) to produced mesons @ high pT. EPOS: K.Werner, F. Liu and T. Pierog, hep-ph/0506232; AKK: S.Albino, B. A. Kniehl, G. Kramer, NPB 725 (2005) 181; KKP: Bernd A. Kniehl, G. Kramer, and B. Potter, Nucl. Phys. B597:337-369, 2001; J. Adams et al. Phys. Lett. B 637:161-169, 2006; STAR Phys. Lett. B616: 8-16, 2005 ZhangbuXu (for STAR) aXiv: 0806.0200 Yichun Xu@Central China Normal University,Wuhan

  4. STAR: PRL97,152301(2006) 2 AB 1 d N / dp d h T R = AB N 2 pp d / dp d  h bin T Baseline for study of RAA in HIC p and p have been limited at 10 and 7 GeV/c in p+p collisions. STAR: Phys. Rev. Lett., 91:072305, 2003 STAR: Phys. Rev. Lett. 97 (2006) 152301 W. Liu etc. Phys. Rev. C77 (2008) 054902 W. Liu etc. Phys. Rev. C 75, 051901 (2007) S.Sapeta etc. Eur.Phys.J.C55:293,2008 Brodsky & AMS PLB 668 111 (2008) parton energy loss? Color charge effect  RAA(p)<RAA(p) Jet conversion? Jet chemistry? Color transparent of direct proton? Yichun Xu@Central China Normal University,Wuhan

  5. Experiment and Data set Tower size: 0.05x0.05 in DfxDh Patch size: 1x1 in DfxDh Data set: EMC Triggers in run5 p+p @ 200GeV Jet Patch trigger:ETtot >6.4GeV(JP) High Tower trigger: ET > 2.5 GeV(HT1) ET > 3.6 GeV(HT2) • Time Projection Chamber (TPC) • Electro-Magnetic Calorimeter (EMC) Yichun Xu@Central China Normal University,Wuhan

  6. pT>3GeV Particle Identification by dE/dx - + Shadowing K± and p(pbar) dE/dx calibration Where Bπis the expected mean dE/dx of p from Bichsel function of ionization energy loss in TPC. Nucl. Instru. & Meth. A 614 (2010) 28–33 Nucl. Instr. & Meth. A 558 (2006) 419 Yichun Xu@Central China Normal University,Wuhan

  7. w/EMC cuts (0.485,0.505) (1.112,1.12) -4 -2 0 2 4 dE/dx re-calibration (I) Yichun Xu@Central China Normal University,Wuhan

  8. s = 0.87 e K p dE/dx re-calibration (II) deviated by 0.4s at high pT/mass Yichun Xu@Central China Normal University,Wuhan

  9. - + STAR preliminary Raw yields extraction : p±/K±/p(p) Peak positions of charged particles are fixed by parameters from re-calibration, and fit is better controlled. Nucl. Instru. & Meth. A 614 (2010) 28–33 Yichun Xu@Central China Normal University,Wuhan

  10. Constraint for pQCD calculation Simon Albino’s private communication Werner Vogelsang p± p(pbar) The trigger bias uncertainty is under study. Our data can provide a better constraint on Fragmentation Function! [1] S.Albino, B. A. Kniehl, G. Kramer, Nucl.Phys.B803:42-104,2008 [2] Daniel de Florian, Rodolfo Sassot and Marco Stratmann, Phys.Rev.D76:074033,2007. [3] STAR Phys. Lett. B616: 8-16, 2005； STAR. Phys. Lett. B 637:161-169, 2006 [4] Yichun Xu, Eur. Phys. J. C (2009) 62: 187-190 [5] Yichun Xu, J. Phys. G: Nucl. Part. Phys. 37 (2010) 094059 Yichun Xu@Central China Normal University,Wuhan

  11. STAR preliminary Particles Ratios in p+p collisions • Experimental data: • (Consistent with published data) • p-/p+, p/p: decrease with pT, indicates a significant quark jet contribution not only to meson but also to baryon. • p/p and p/p: p/p+~0.2, and p/p-~0.1 • Compare to models: • PYTHIA(v6.205) describe ratios reasonably. • DSS over-predicts anti-protons relative to pions and protons. The trigger bias uncertainty is under study. Yichun Xu, Eur. Phys. J. C (2009) 62: 187-190 J. Phys. G: Nucl. Part. Phys. 37 (2010) 094059 STAR. Phys. Lett. B 637:161-169, 2006 STAR Phys. Lett. B 616: 8-16, (2005) 8 Yichun Xu@Central China Normal University,Wuhan

  12. Barrel Electro-Magnetic Calorimeter Triggered by tower p K0S STAR preliminary K0S at high pT (EMC as hadron trigger) K0S→p++p-(trigger) a factor of100 enhancement Given pT=5 GeV/c,~5.6MHT1 triggered events are equivalent to L(0.64 pb-1)*s(30mb)*effTrg(3%)/effTrk(90%) ~600Mminibias events. Yichun Xu@Central China Normal University,Wuhan

  13. STAR preliminary Comparison of K0S signal RunV 5.6M EMC trigger events RunII 10.26M minibias events Mark Heinz, Ph. D thesis,2005 Yichun Xu@Central China Normal University,Wuhan

  14. STAR Preliminary r0 & L(Lbar) at high pT 8<pT<10 GeV/c Yichun Xu@Central China Normal University,Wuhan

  15. Summary • Two new methods for PID have been developed: dE/dx re-calibration and EMC hadron trigger. • Extend identified hadron spectra up to15 GeV/c. • Provide constraints for Fragmentation Function. • Indicate a significant quark jet contribution to baryon from decrease of pbar/p with pT . • Provide baseline for nuclear modification factor in HIC How the gluon /quark jet interact with the medium. Yichun Xu@Central China Normal University,Wuhan

  16. Yichun Xu@Central China Normal University,Wuhan

  17. <1 Jet Conversion & Jet hadrochemistry Enhanced parton splitting in medium Jet parton scatters on medium parton and changes flavor. q + qbar  g + g q(qbar) + g  g + q(qbar) Enhance p/ and K/ ratios in A+A jets for LHC S.Sapeta and U.A. Wiedemann, arXiv:0707.3494 W. Liu, R.J. Fries, Phys. Rev. C77 (2008) 054902 Yichun Xu@Central China Normal University,Wuhan W. Liu, C.M. Ko, B.W. Zhang, Phys. Rev. C 75, 051901 (2007)

  18. Color transparent of direct proton Brodsky & AMS PLB 668 111 (2008) Anne M. Sickles @QM2009 Yichun Xu@Central China Normal University,Wuhan

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