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Identified hadron spectra at high-p T

This presentation explores the basic properties of QCD relevant to us, focusing on high-pT hadron spectra and fragmentation functions in e+e- and p+p collisions. New measurements at RHIC compile data on jet chemistry, effective gluon color charge, and more. The conclusion and outlook consider the implications of these findings.

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Identified hadron spectra at high-p T

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  1. Identified hadron spectra at high-pT Basic properties of QCD relevant to us Fragmentation Function in e+e- and p+p New Measurements at RHIC Compile RHIC data on jet chemistry Extract effective gluon Color Charge at RHIC Conclusion and Outlook Zhangbu Xu, QM08, Jaipur, India

  2. Journey to the West (QM08 India) • Many Versions of Models of QGP Buddhism in China (jet quenching) • True teaching QCD theory • Pilgrimage Experiments to India (LHC, RHIC, SPS, AGS) • 16 years (629—646) RHIC 1992—2008 • Ancient University Jaipur, India(Nalanda) • Slip through the gate illegal immigrant without passport 玄奘 Tripitaka (602—664) Zhangbu Xu, QM08, Jaipur, India

  3. Fundamentals of QCD relevant to our field T.D. Lee, 1995 • Quark Confinement • Symmetry Breaking Gluons carry color-charge Asymptotic Freedom Zhangbu Xu, QM08, Jaipur, India

  4. Color Factors QCD : For SU(3) : Nc = 3 CA = 3, CF = 4/3 CA/CF=9/4 CF ~ strength of a gluon coupling to a quark CA ~ strength of the gluon self coupling TF ~ strength of gluon splitting into a quark pair Zhangbu Xu, QM08, Jaipur, India

  5. path length L Eg hard parton ~ 9/4 Eq 2 D E <q> ^ L  a C s Energy Loss and QCD One mechanism of energy loss : Medium induced gluon radiation  C Experimentally observable (of Eloss) related to basic ingredient of QCD - Gauge Group through Color Factors Or extracting an effective Color Factor S. Wicks et al, nucl-th/0512076 M. Gyulassy et al., PRL 85 (2000) 5535 R. Baier et al., NPB 483 (1997) 291 Zhangbu Xu, QM08, Jaipur, India

  6. Consequence of CA/CF=9/4 in A+A WHDG, arXiv:nucl-th/0512076 Other models: S. Wicks, I. Vitev, QM08 Zhangbu Xu, QM08, Jaipur, India

  7. PYTHIA provided by Adam Kocoloski gq qq gg Processes in hadron-hadron collisions PDFParton 2->2 Fragmentation functions Zhangbu Xu, QM08, Jaipur, India

  8. Fragmentation Functions • Will these ingredients be sufficient for p+p collisions? • How will p+p collisions provide additional information for our understanding of QCD and for model developments • What will be modified in A+A collisions • FF • Running of aS • Effective Color Charge factor Zhangbu Xu, QM08, Jaipur, India

  9. PID at high-pT (where do we start?) Where it begins My talk: pT>5 GeV/c Zhangbu Xu, QM08, Jaipur, India

  10. Sources of high pT hadrons : quarks or gluons Ng(i)/ (Ng(i) + Nq(i)); i = , K, p… At high pT range measured : Large gluon contribution (~ 90%) to produced baryons Substantial quark contribution (~ 40%) to produced mesons STAR : PLB 637 (2006) 161 S. Albino et al, NPB 725 (2005) 181 B. Mohanty (for STAR) nucl-ex/0705.9053 L. Ruan (for STAR) nucl-ex/0701070 and WWND Zhangbu Xu, QM08, Jaipur, India

  11. Global Fit In principle, allow to separate quark-to-proton and anti-quark-to-proton fragmentation functions The best constraint on the gluon fragmentation function Dgp at large values of z currently available. 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 Zhangbu Xu, QM08, Jaipur, India

  12. Extend Charged hadron spectra! P. Fachini, QM08 Y.C. Xu, DNP07 Zhangbu Xu, QM08, Jaipur, India

  13. Comparison with pQCD Not all models are equal! • Clear flavor dependence • DSS NLO overpredicts pbar yield • Best constraint on gluon/quark-to-proton fragmentation functions at high z Zhangbu Xu, QM08, Jaipur, India

  14. Quark vs gluon from hadron suppression STAR, B. Mohanty STAR, P. Fachini PRL 97, 152301 (2006) STAR Preliminary Curves: X-N. Wang et al PRC70(2004) 031901 No sign of stronger gluon energy loss in p/p or p/p ratios X.N. Wang and X.F. Guo, NPA 696(2001)788 T. Renk and K. Eskola, PRC 76 (2007)027901 W. Liu, C.M. Ko, B.W. Zhang, nucl-th/0607047 Need good understanding of how quarks and gluons turn into hadrons Zhangbu Xu, QM08, Jaipur, India

  15. More news: J/ at high-pT • Investigate heavy quarkonium production mechanism and hadronization • In p+p collision • Gluon fusion • Charm fragmentation • Feed down • In heavy ion collision • Gluon energy loss • Heavy quark energy loss • Hot-wind dissociation in QGP Zebo Tang (STAR) QM08 J/-h correlation to understand J/ production mechanism Zhangbu Xu, QM08, Jaipur, India

  16. pT>5 GeV/c 4<pT<5 GeV/c Jet Chemistry in p+p Zhangbu Xu, QM08, Jaipur, India

  17. STAR whitepaper Thermal distribution among hadrons Low-pT integrated yields • Statistical Mechanics describes the relative particle abundances • This happens at the phase boundary (T=165+-10MeV) Zhangbu Xu, QM08, Jaipur, India

  18. Nuclear Modification Factor P. Fachini (STAR) • Same RAA for ,, • Different RAA for pbar,p,Ks, e(NPE) Zhangbu Xu, QM08, Jaipur, India

  19. Effective Color Factor Simple Algebra: a1dEq+b1dEg ----------------- = a2dEq+b2dEg 10%+90%C ----------------- = RAA(p/p) 60%+40%C 100% ----------------- = RAA(e/p) 60%+40%C Zhangbu Xu, QM08, Jaipur, India

  20. ALEPH : ZPC 76 (1997) 1 OPAL :EJPC 20 (2001) 601 SU(3) is the gauge group for QCD S = 0.119 Extract effective Color Factors Zhangbu Xu, QM08, Jaipur, India

  21. High-pT J/ Dissociation or not? • Double the pT range to 10GeV/c • Consistent with no suppression at high pT: RAA(pT>5 GeV/c) = 0.9±0.2 • Low pT: RAA(pT<4 GeV/c) = ~0.5 • Indicates RAA increase from low pT to high pT • Most models expect a decrease RAA at high pT: AdS/CFT: • H. Liu, K. Rajagopal and U.A. Wiedemann, • PRL 98, 182301(2007) and hep-ph/0607062 • Two Component Approach: • X. Zhao and R. Rapp, hep-ph/07122407 • private communication Zebo Tang (STAR), QM08 Zhangbu Xu, QM08, Jaipur, India

  22. Color Transparency and direct hadron? 1) proton RAA>pion RAA 2) J/ RAA~=1 (Cu+Cu) pT>5 GeV/c A different term for quark coalescence? Go to higher pT and vector meson? Zhangbu Xu, QM08, Jaipur, India

  23. path length L path length L hard parton hard parton Convert to Effective CA/CF 20%+80%C ----------------- = RAA(KS0/p) 60%+40%C Conversion probability can be absorbed into C: <= W. Liu, R.J. Fries, arXiv:0801.0453[nucl-th] Zhangbu Xu, QM08, Jaipur, India

  24. Constraints on Opacity • Look at data in a quantitative way • Geometry and evolution, dE/dx model • How the gluon and quark compositions change with dE/dx? • Different PID and global constraints on initial jet composition PHENIX: WHDG RAA (C,dEq,pT,FF) Zhangbu Xu, QM08, Jaipur, India

  25. Probing quark dominated jet production at lower energy to gluon dominated jet • production at higher energy • Heavy-Flavor tag • g+jet • pbar-pbar IAA Outlook - Energy Dependence Similar Eloss for quarks and gluons QCD type (color charge effect) Eloss Wang et al., PRC 58 (1998) 2321 Wang et al., PRC 71 (2005) 014903 B. Mohanty, ISMD2007 Zhangbu Xu, QM08, Jaipur, India

  26. Conclusions • A large dataset extended to higher momentum with many identified particles in p+p and A+A collisions • Effective gluon color charge factor<9/4 • Modeling flavor and color charge effectsRAA (C,dEq,pT,FF) QED FQHE(perfect fluid) Chern-Simon QCDsQGP (perfect Liquid) ? Zhangbu Xu, QM08, Jaipur, India

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