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Jet Quenching: What it really measures?

Jet Quenching: What it really measures?. Xin-Nian Wang Lawrence Berkeley National Laboratory. High-pT physics at LHC, Jyvaskyla, March 21-27,2007. Jet Quenching in A+A Collisions. leading particle. hadrons. q. q. hadrons. leading particle. Leading particle suppressed. hadrons. q. q.

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Jet Quenching: What it really measures?

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  1. Jet Quenching: What it really measures? Xin-Nian Wang Lawrence Berkeley National Laboratory High-pT physics at LHC, Jyvaskyla, March 21-27,2007

  2. Jet Quenching in A+A Collisions leading particle hadrons q q hadrons leading particle Leading particle suppressed hadrons q q hadrons N-N collision A-A collision leading particle suppressed Comparative study of jet quenching schemes; A. Majumder QM06

  3. Gyulassy-Levai-Vitev (GLV) • Operator formalism that sums order by order in opacity M. Gyulassy, P. Levai, I. Vitev, Nucl.Phys.B571:197,2000; Phys.Rev.Lett.85:5535,2000; Nucl.Phys.B594:371,2001; Phys. Lett.B538:282-288,2002.

  4. Twist Expansion • Expansion in higher-twist operator of multiple parton scattering X. Guo, X. N. Wang, Phys. Rev. Lett. 85:3591 (2000); X. N. Wang, X. Guo, Nucl. Phys. A. A696:788, (2001); E. Wang, X. N. Wang, Phys. Rev. Lett.87, 142301,(2001); ibid 89 162301 (2002); B. Zhang, X.N.Wang, Nucl.Phys. A720:429-451,2003.

  5. Armesto-Salgado-Wiedeman (ASW) U. Wiedemann, Nucl. Phys. B.582, 409 (2000); ibid. 588, 303 (2000), Nucl. Phys. A.690 (2001); C. Salgado, U. Wiedemann, Phys.Rev. D. 68 014008 (2003); K. Eskola, H. Honkanen, C. Salgado, U. Wiedemann, Nucl. Phys. A.747, 511(2005); N. Armesto, C. Salgado, U. Wiedemann, Phys.Rev.D.72,064910 (2005). • Path integral in opacity with summation of many soft scatterings, dipole model of the parton interaction with medium

  6. Arnold-Moore-Yaffe (AMY) P. Arnold, G. Moore, L. Yaffe, JHEP 0111:057,2001; ibid 0112:009,2001; ibid. 0206:030, 2002; S. Jeon, G. Moore Phys. Rev. C71:034901,2005; S.Turbide, C.Gale, S. Jeon, G. Moore, Phys. Rev. C72:014906,2005. • Finite temperature field theory approach, transport equation for leading parton with HTL resumed interaction

  7. Energy Loss in Twist Expansion

  8. Gluon distribution of the medium

  9. pT broadening and gluon distribution k=E q p

  10. Elastic Energy Loss +…. + +

  11. Elastic Energy Loss

  12. Interference effect in elastic energy loss XNW nucl-th/0604040

  13. Radiative energy loss +…. + +

  14. Radiative vs elastic energy loss For E=10 GeV, T=0.2 GeV, L=6 fm, as=0.3

  15. Quark-quark Scattering

  16. q-hat and shear viscosity h Majumder, Muller and XNW (hep-ph/0703082) Shear viscosity Tested against different transport calculations of h and q-hat, Either through collisions or color field fluctuations Jet quenching 

  17. Fragility of single hadron suppression Eskola et al., hep-ph/0406319 Robustness of jet quenching as probes?

  18. NLO pQCD Calculation NLO (Next to Leading Order ): Jet quenching in 2→3 processes Zhang, Owens, Enke Wang and XNW (nucl-th/0701045 )

  19. Single hadron spectra

  20. Modification Factor RAA

  21. Surface emission?

  22. Fragility of single hadron suppression

  23. Centrality dependence of RAA

  24. Surface vs. Volume

  25. Dihadron sensitivity

  26. Centrality Dependence PRL95(2005)152301

  27. Centrality Dependence PRL95(2005)152301

  28. Dihadron suppression

  29. Sensitivity to initial density

  30. q-hat in a nucleus e- Enke Wang & XNW PRL 89, 162301(2002)

  31. Conclusions • Jet quenching measures q-hat- gluon distribution of the medium • Elastic energy loss negligible • qhat  viscosity • NLO pQCD analysis of jet quenching • both single and dihadrons • RAANLO < RAALO • Sensitivity of single and dihadron suppression to the initial gluon density • Centrality dependence of single and dihadron suppression • Single hadron suppression become fragile while dihadron suppression is more robust probe at LHC

  32. Modified Fragmentation Functions 1-D expanding Transport coefficient Energy loss parameter

  33. LO pQCD of high pT hadron spectra 2→2 processes Jet quenching in 2→2 processes A factor K=1.5-2 account for higher order corrections

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