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Why GLR-MQ-ZRS equation is necessary for understanding STAR BES program?

Wei Zhu East China Normal University KITPC  20 12 . 07. Why GLR-MQ-ZRS equation is necessary for understanding STAR BES program?. Nuclear suppression factor. Unintegrated distribution=TMD. =TMD. Reasons. 1. Integrated and unintegrated gluon distributions can not directly

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Why GLR-MQ-ZRS equation is necessary for understanding STAR BES program?

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  1. Wei Zhu East China Normal University KITPC 2012.07. Why GLR-MQ-ZRS equation is necessary for understanding STAR BES program?

  2. Nuclear suppression factor

  3. Unintegrated distribution=TMD =TMD

  4. Reasons 1. Integrated and unintegrated gluon distributions can not directly measured, they only can been extracted from data using QCD evolution equations. 2. 3. We need a QCD evolution equation, which includes nuclear shadowing and antishadowing effects.

  5. Why not? • DGLAP Equation. Nuclear shadowing and antishadowing effects are assumed in input by hand.

  6. Why not • BFKL equation, It works at x< and has not nonlinear corrections. • BK equation=BFKL+gluon fusion. It works at x< and does not consider the antishadowing corrections. • .

  7. JIMWLK equation • Although it predicts the saturation at small x limit, however, can not describe the parton distributions at < x<1.

  8. Only GLR-MQ-ZRS Equation1983 version • L.V. Gribov, E.M. Levin and M.G. Ryskin, Phys. Rep.100 (1983) 1.

  9. Fusion Corrections of Gluon Fusion DGLAP DGLAP GLR-MQ-ZRS to 3

  10. Abramovsky, Gribov and Kancheli, Cutting rule (1973) 1 -4 2

  11. 1986 version • A.H. Mueller and J. Qiu, Nucl. Phys. B268 (1986) 427.

  12. W. Zhu, Nucl. Phys. B551 (1999) 245. W. Zhu and J.H.Ruan, Nucl. Phys. B559 (1999) 378; W. Zhu and Z.Q. Shen, HEP$\&$ NP, 29 (2005) 109. 1999 version

  13. ZRS versionTOPT cutting rule

  14. TOPT Cutting Rules • F.E. Close, J. Qiu and R.G. Roberts, Phys. Rev. D 40 (1989) 2820. • W. Zhu, Nucl. Phys. B551, 245 (1999). • W. Zhu and J.H. Ruan, Nucl. Phys. B559, 378(1999). • W. Zhu, Z.Q. Shen and J.H. Ruan, Nucl. Phys. B692, 417 (2004);

  15. TOPT-Cutting rule • List all possible TOPT diagrams with different cuts. • The contributions of the cut diagrams • have the identical integral kernel with only the following different factors R:

  16. (a)The sign in the first factor is determined by the energy deficits; • (b)The second factor takes a value of 1/2 if the probe-vertex inserts in the initial line; • (c) function relates to the probe vertex.

  17. Recombination functions

  18. 4. Twist-4 level (collinear frame) CVPT generalize Mueller-Qiu (1986) to whole x region

  19. TOPT:Zhu, Ruan (1999); Bluemlein, Ravindran, Ruan, Zhu (2001); Zhu,Shen (2004)

  20. Spin-dependent gluon recombination function

  21. Why yes? • GLR-MQ-ZRS equation has solid QCD basic. • LL(Q^2). 0.001<x<1. • DLL(1/x,Q^2). 0.001<0.1-0.2

  22. GLR-MQ-ZRS at small x

  23. Cronin Effect

  24. Nuclear modification factor

  25. KMR Scheme

  26. Nuclear shadowing and antishadowing effects • A+A(for gluon)>p+A(for gluon) • ~eA(for gluon)>eA(for quarks) • Contributions of the gluon fusion at initial state are inescapable in RHIC and LHC physics.

  27. ?

  28. ? ???

  29. arXiv:1012.4224W. Zhu, J.H. Ruan and F.Y. Hou • A rapid crossover from week energy • loss to strong energy loss at a universal critical energy of gluon jet Ec ∼ 10GeV

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