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Jet Quenching at RHIC 喷注淬灭

Jet Quenching at RHIC 喷注淬灭. 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 Other unique features of QCD jet quenching Conclusion and Outlook.

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Jet Quenching at RHIC 喷注淬灭

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  1. Jet Quenching at RHIC喷注淬灭 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 Other unique features of QCD jet quenching Conclusion and Outlook Zhangbu Xu, USTC 2008

  2. Fundamentals of QCD relevant to our field T.D. Lee, 1995 • Quark Confinement 夸克禁锢 • Symmetry Breaking对称破缺 Gluons carry color-charge Asymptotic Freedom Zhangbu Xu, USTC 2008

  3. 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 as 藕合常数 Zhangbu Xu, USTC 2008

  4. 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, USTC 2008

  5. Features of QCD energy loss • Color factor and coupling constant • Pathlength L2 dependence • Deadcone • Jet chemistry and Jet Conversion • Mach Cone 1982: J. D. Bjoken: Fermilab-pub-82/59-THY Energy loss in elastic scattering 1992/1995: X.-N. Wang, M. Gyulassy: PRL68(92) 148, PRD45 (92)844, NPB420(94)583, PRD51(95)3436 Energy loss is dominated by gluon radiation 1995/1997: BDMPS (R. Baier, Yu. L. Dokshitzer, A. Mueller, S. Peigue, D.Schiff) :PLB345(95) 277, NPB478(96)577,NPB483(97)291,NPB484(97)265 Gluon multiple scattering and gluon radiation 2000: GLV(M. Gyulassy, P. Levai, I. Vitev): PRL85(00)5535, NPB594(01)371 U. Wiedemann: NPB588(2000)303 Opacity expansion 2001/2002: E. Wang, X.-N. Wang: PRL87(01)142301, PRL89(02)162301 Detailed Balance; Jet Tomography 2001/2009 Y. Dokshitzer & D. Kharzeev PLB 519(2001)199; S. Wicks et al, nucl-th/0512076 Zhangbu Xu, USTC 2008

  6. Consequence of CA/CF=9/4 in A+A (AA/pp) QGP内高能部分子能损前后的空间分布 q/g~=9/4 Other models: S. Wicks, I. Vitev, QM08 WHDG, arXiv:nucl-th/0512076 Zhangbu Xu, USTC 2008

  7. PYTHIA provided by Adam Kocoloski gq qq gg Processes in hadron-hadron collisions PDFParton 2->2 Fragmentation functions 部分子分布函数(PDF)部分子作用截面碎裂函数 Zhangbu Xu, USTC 2008

  8. 我们需要的量 • 核子内部分子分布函数(PDF)理论函数(CTEQ6M)拟合实验数据(e+p) • 部分子作用截面和出射动量 二次展开的微挠色动力学(NLO pQCD) • 碎裂函数(喷注中强子的分布) • 只取喷注中大动量的单个强子 • 没有重建原始部分子 • 理论函数(DSS)拟合实验数据(e+e-,e+p,p+p) • 部分子在QGP中的能损机制 Zhangbu Xu, USTC 2008

  9. 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 喷注中强子的分布 Zhangbu Xu, USTC 2008

  10. PID at high-pT (where do we start?) Where it begins My talk: pT>5 GeV/c Zhangbu Xu, USTC 2008

  11. 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, USTC 2008

  12. 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, USTC 2008

  13. Extend Charged hadron spectra! P. Fachini, QM08 Y.C. Xu, DNP07 Zhangbu Xu, USTC 2008

  14. 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, USTC 2008

  15. 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 质子和介子在QGP强子压底前后的比值 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, USTC 2008

  16. 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) 强子的热统分布: 温度和化学势 Zhangbu Xu, USTC 2008

  17. pT>5 GeV/c 4<pT<5 GeV/c Jet Chemistry in p+p 高动量强子化学分布 强子来源和QGP作用下的变化 Zhangbu Xu, USTC 2008

  18. 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, USTC 2008

  19. 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, USTC 2008

  20. 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, USTC 2008

  21. Constraints on Opacity (QGP透明度 ) • 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, USTC 2008

  22. Probing quark dominated jet production at lower energy to gluon dominated jet • production at higher energy • Heavy-Flavor tag • g+jet • pbar-pbar IAA (T. Renk) Similar Eloss for quarks and gluons Outlook - Energy Dependence 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, USTC 2008

  23. Di-hadron Single y (fm) y (fm) x (fm) x (fm) Less surface bias Limited sensitivity of RAA to P(E,E) T. Renk, PRC 74 (2006) 034906 T. Renk and Eskola,hep-ph/0610059 2IAA 2RAA Di-hadron correlations more robust probes of initial density ~ H. Zhong et al., PRL 97 (2006) 252001 Advantage of Di-hadron Correlations双强子关联 Zhangbu Xu, USTC 2008

  24. 光子—强子关联 Study the particles distribution in fractional energy of ’s energy  2 0 180° No track with p>3GeV/c points to the trigger tower Leading particle • Use Transverse Shower Profile for /0 identification. • 光子无能损,可用来标定与其关联的喷注的原初能量 BEMC TPC Beam axis Zhangbu Xu, USTC 2008

  25. 光子—强子角关联的试验分布 -rich sample versus 0-rich sample • The -rich sample has lower near-side yield than 0. Zhangbu Xu, USTC 2008

  26. Jet X.-N. Wang et al PRL 77(1996)231 • 1st measurement of away-side -h correlations • Suppression similar level as inclusives in central collisions Note : Ejet = E Promptg Eloss probability distribution : -hadron correlation • Provides constraints on Eloss probability distributions • Possibly gives full accounting of jet energy loss Zhangbu Xu, USTC 2008

  27. 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, USTC 2008

  28. 作业题 I 计算喷注淬灭能损后(反质子/介子)的比值 假设p/p=0.25 in p+p, p 100% from gluon, p 30% from gluon, 70% from quark 而且认为SU(3) (pQCD)可适用 • >1 • [0.25,1] • [0.01,0.25] • <0.01 Zhangbu Xu, USTC 2008

  29. 作业题 II 2）喷注淬灭能损后的能量跑哪儿去？ 3）喷注淬灭能损（dE/dx) 和 带电粒子穿过探测器的能损比较。 Zhangbu Xu, USTC 2008

  30. Nuclear Modification Factor P. Fachini (STAR) • Same RAA for ,, • Different RAA for pbar,p,Ks, e(NPE) Zhangbu Xu, USTC 2008

  31. Enhanced correlated yield at large  on near side Away side shape modification 2.5 < pTtrig< 4 GeV/c 1< pTassoc < 2.5 GeV/c d+Au Au+Au Medium response STAR: PRL 95 (2005) 152301 J.G. Ulery, QM 2005 STAR : J. Putschke, QM2006 STAR : M. J. Horner, QM2006 pTtrig=3-6 GeV/c, 2 GeV/c <pTassoc< pTtrig Reappearance of di-jets STAR : PRL 97 (2006) 162301 Current Observations in STAR High pT suppression Away side yield modification Parton Eloss pTlp : 4 - 6 GeV/c STAR : PLB 655 (2007) 104 STAR : PRL 97 (2006) 152301 STAR : PRL 91 (2003) 072304 pTasoc : 2 GeV/c - pTlp What does these features reveal about the medium ? Zhangbu Xu, USTC 2008

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