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Zhangbu Xu, QM08, Jaipur, India 1 Identified hadron spectra at high-p T 1.Basic properties of QCD relevant to us 2.Fragmentation Function in e + e - and.

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Presentation on theme: "Zhangbu Xu, QM08, Jaipur, India 1 Identified hadron spectra at high-p T 1.Basic properties of QCD relevant to us 2.Fragmentation Function in e + e - and."— Presentation transcript:

1 Zhangbu Xu, QM08, Jaipur, India 1 Identified hadron spectra at high-p T 1.Basic properties of QCD relevant to us 2.Fragmentation Function in e + e - and p+p 3.New Measurements at RHIC 4.Compile RHIC data on jet chemistry 5.Extract effective gluon Color Charge at RHIC 6.Conclusion and Outlook

2 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)

3 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

4 Zhangbu Xu, QM08, Jaipur, India 4 Color Factors QCD : For SU(3) : N c = 3 C A = 3, C F = 4/3 C F ~ strength of a gluon coupling to a quark C A ~ strength of the gluon self coupling T F ~ strength of gluon splitting into a quark pair C A /C F =9/4

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

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

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

8 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 1.FF 2.Running of  S 3.Effective Color Charge factor

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

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

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

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

13 Zhangbu Xu, QM08, Jaipur, India 13 Comparison with pQCD 1.Clear flavor dependence 2.DSS NLO overpredicts pbar yield 3.Best constraint on gluon/quark-to-proton fragmentation functions at high z Not all models are equal!

14 Zhangbu Xu, QM08, Jaipur, India 14 Quark vs gluon from hadron suppression 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 PRL 97, 152301 (2006) STAR Preliminary No sign of stronger gluon energy loss in p/  or p/p ratios Need good understanding of how quarks and gluons turn into hadrons STAR, B. Mohanty STAR, P. Fachini Curves: X-N. Wang et al PRC70(2004) 031901

15 Zhangbu Xu, QM08, Jaipur, India 15 More news: J/  at high-p T Zebo Tang (STAR) QM08 J/  -h correlation to understand J/  production mechanism 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

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

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

18 Zhangbu Xu, QM08, Jaipur, India 18 Nuclear Modification Factor P. Fachini (STAR) 1.Same R AA for , ,  2.Different R AA for pbar,p,Ks, e(NPE)

19 Zhangbu Xu, QM08, Jaipur, India 19 Effective Color Factor a 1  E q +b 1 dE g ----------------- = a 2  E q +b 2  E g 10%+90%C ----------------- = R AA (  p/  ) 60%+40%C 100% ----------------- = R AA (e/  ) 60%+40%C Simple Algebra:

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

21 Zhangbu Xu, QM08, Jaipur, India 21 High-p T J/  Dissociation or not? Double the p T range to 10GeV/c Consistent with no suppression at high p T : R AA (p T >5 GeV/c) = 0.9±0.2 Low p T : R AA (pT<4 GeV/c) = ~0.5 Indicates R AA increase from low p T to high p T Most models expect a decrease R AA at high p T : 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

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

23 Zhangbu Xu, QM08, Jaipur, India 23 Convert to Effective C A /C F hard parton path length L hard parton path length L 20%+80%C ----------------- = R AA (K S 0 /  ) 60%+40%C Conversion probability can be absorbed into C: <= W. Liu, R.J. Fries, arXiv:0801.0453[nucl-th]

24 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 R AA (C,  E q,p T,FF)

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

26 Zhangbu Xu, QM08, Jaipur, India 26 Conclusions QED  FQHE(perfect fluid)  Chern-Simon 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 effects R AA (C,  Eq,pT,FF) QCD  sQGP (perfect Liquid)  ?

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