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Investigating jet chemistry at RHIC through identified hadron compositions from p+p to Au+Au

Investigating jet chemistry at RHIC through identified hadron compositions from p+p to Au+Au. Yichun Xu ( 许依春 ) for the STAR Collaboration Center for Particle Physics and Technology University of Science and Technology of China. Outline. Motivation

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Investigating jet chemistry at RHIC through identified hadron compositions from p+p to Au+Au

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  1. Investigating jet chemistry at RHIC through identified hadron compositions from p+p to Au+Au Yichun Xu (许依春) for the STAR Collaboration Center for Particle Physics and Technology University of Science and Technology of China QCD phase transition and RHIC

  2. Outline • Motivation • In p+p, extend identified hadron spectra up to higher pT. • Good constraints to pQCD calculation. • Baseline for study of nuclear modification factor in HIC. • In Au+Au, study of nuclear modification factor (RAA) • Color charge effect, Jet conversion, Jet hadrochemistry • Data analysis • Identify charged p, K, p(p) by ionization energy loss (dE/dx) • Reconstruct K0Sp++p-with one triggered pion • Results & Summary QCD phase transition and RHIC

  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. J. Adams et al. Phys. Lett. B 637:161-169, 2006; Z. Xu (for STAR) arXiv:0806.0200 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; EPOS: K.Werner, F. Liu and T. Pierog,hep-ph/0506232; QCD phase transition and RHIC

  4. STAR: PRL97,152301(2006) 2 AB 1 d N / dp d h path length L Eg T R hard parton = AB N 2 pp d / dp d  h ~ 9/4 In pQCD: bin T Quark Eq Quark Baseline for study of RAA in HIC Color charge effect of parton energy loss RAA(p)<RAA(p) QCD phase transition and RHIC

  5. <1 Jet Conversion & Enhanced parton splitting 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 energy. W. Liu, R.J. Fries, Phys. Rev. C77 (2008) 054902 S.Sapeta and U.A. Wiedemann, Eur.Phys.J.C55:293-302,2008 QCD phase transition and RHIC W. Liu, C.M. Ko, B.W. Zhang, Phys. Rev. C 75, 051901 (2007)

  6. Experiment and Data set 0.05rad(Df)x0.05(Dh) Near-side Away-side Data set: EMC Triggers in run5 pp @ 200GeV Jet Patch trigger:ETtot >6.4GeV High Tower trigger: ET > 2.5 GeV ET > 3.6 GeV • Time Projection Chamber (TPC) • Electro-Magnetic Calorimeter (EMC) QCD phase transition and RHIC

  7. STAR preliminary p±/K±/p(pbar) with dE/dx (away-side) - + pT>3GeV 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 QCD phase transition and RHIC

  8. Barrel Electro-Magnetic Calorimeter Triggered by tower p K0S STAR preliminary Triggered K0S at high pT (near-side) K0S→p++p-(trigger) A factor of 100 enhancement Given pT=5 GeV/c,~5.6MHT1 triggered events are equivalent to L(0.64 pb-1)*s(30mb)*effTrg(3%)/effTrk(90%) ~600Mminimum bias events. QCD phase transition and RHIC

  9. STAR preliminary Comparison of K0S signal RunV 5.6M EMC trigger events RunII 10.26M minimum bias events From Mark Heinz thesis QCD phase transition and RHIC

  10. Constraint for pQCD calculation (I) STAR preliminary • First extend particle spectra up to 15 GeV/c in p+p collisions. • pQCD NLO calculations are consistent with charged pion spectra • 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, arXiv: 0707.1506 [hep-ph]; Phys.Rev.D76:074033,2007. DSS Fragmentation Functions –provided by W. Vogelsang QCD phase transition and RHIC

  11. Constraint for pQCD calculation (II) • Compare to published data: • (Consistent with published data) • p-/p+, pbar/p,K-/K+ • decrease with increasing pT indicates relatively higher valence quark contribution to p+, K+, p than to p-, K-, pbar. • 2. p/p+ ~0.2, pbar/p-~0.1 • K±/p±~ K0S/p± • no trigger bias • Compare to models: • Both can describe p-/p+, but deviate other ratios • DSS over-predicts pbar, K- relative to p, K+ and p • AKK over-predicts proton under-predicts pbar. STAR preliminary J. Adams et al. Phys. Lett. B 637:161-169, 2006 QCD phase transition and RHIC

  12. RAA for p, K±+p(pbar), K0S and r0 • RAA(p)~RAA(K0S)~ RAA(r0) despite the differences in quark flavor composition and mass at high pT . • RAA(K++p)~ RAA(K-+pbar) despite the different contributions from gluon and quark jets and the effect of the Casimir factor on jet energy loss • 3. Jet conversion’s RAA(K0S) > measure •  kaon spectra in p+p w/ FF in model •  Original RAA(K0S) w/o jet conversion was assumed to be equal to RAA(p). • 4. Enhanced parton splittingRAA(r0)~RAA(p) • 5. Require Quantitative modeling and calculationsincorporating 3D hydrodynamics in an expanding medium and the proper FFs. STAR preliminary W. Liu, R.J. Fries, Phys. Rev. C77 (2008) 054902; W. Liu, C.M. Ko, B.W. Zhang, Phys. Rev. C 75, 051901 (2007) QCD phase transition and RHIC

  13. Summary Thanks for your attention! p+p collisions: • Extend identified hadron spectra up to 15 GeV/c in p+p. • Anti-particle/particle indicates relatively higher valence quark contribution to p+, K+, p than to p-, K-, pbar. • Provide constraints for Fragmentation Function. Au+Au collisions: • Color charge effect can not explain RAA(K++p)~ RAA(K-+pbar) and RAA(p)~RAA(K0S)~ RAA(r0) • The prediction of RAA(K0S) with Jet Conversion in central Au+Au collisions is higher than our measurements. • Enhanced parton splitting can not explainRAA(r0)~RAA(p). • Require Quantitative modeling and calculations incorporating3D hydrodynamicsin an expanding medium and theproper FFs. QCD phase transition and RHIC

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