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Hard probes at RHIC and LHC Magdalena Djordjevic Ohio State University

Hard probes at RHIC and LHC Magdalena Djordjevic Ohio State University. Heavy ion physics has a goal to form and observe a QGP. Is the QGP already discovered at RHIC?. Jet Quenching of light partons strongly suggest that QGP is discovered .

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Hard probes at RHIC and LHC Magdalena Djordjevic Ohio State University

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  1. Hard probes at RHIC and LHC Magdalena Djordjevic Ohio State University

  2. Heavy ion physics has a goal to form and observe a QGP. Is the QGP already discovered at RHIC? • Jet Quenching of light partons strongly suggest that QGP is discovered. • Further tests of jet tomography using heavy quarks could be decisive as a complementary test of the theory. Heavy mesons not yet measured at RHIC. However, single electron measurements are available.

  3. Single electron suppression measurements at RHIC V. Greene, S. Butsyk, QM2005 talks J. Dunlop, J. Bielcik; QM05 talks Significant reduction at high pT suggest sizable energy loss! Can this be explained by the energy loss in QGP?

  4. Outline Radiative energy loss mechanisms. Heavy meson (D and B) and single electron suppression. B mesons can not be neglected in the computation of single electron spectra. Radiative energy loss alone can not explain the experimental data. Inclusion of elastic energy loss as a solution? Is elastic energy loss important at LHC?

  5. c, b Single electron suppression D, B e- 1) production 2) medium energy loss 3) fragmentation 4) decay 1) Initial heavy quark pt distributions 2) Heavy quark energy loss 3) c and b fragmentation functions into D, B mesons 4) Decay of heavy mesons to single e-. To make theoretical predictions for heavy meson and single electron suppression we generalized the GLV method (PLB538:282,2002).

  6. Initial heavy quark pt distributions To compute the initial charm and beauty pt distributions we applied the MNR code (Mangano et al. Nucl.Phys.B373,295(1992)). Parameters values from R.Vogt, Int.J.Mod.Phys.E 12,211(2003).

  7. c c L • Radiative heavy quark energy loss • Three important medium effects control the radiative energy loss: • Ter-Mikayelian effect (M. D. and M. Gyulassy, Phys. Rev. C 68, 034914 (2003)) • Transition radiation (M. D., to be published). • Energy loss due to the interaction with the medium (M. D. and M. Gyulassy, Phys. Lett. B 560, 37 (2003); Nucl. Phys. A 733, 265 (2004)) 1) 2) 3)

  8. c Energy loss due to the interaction with the medium Caused by the multiple interactions of partons in the medium. To compute medium induced radiative energy loss for heavy quarks we generalize GLV method, by introducing both quark M and gluon mass mg.

  9. + + This leads to the computation of the fallowing types of diagrams: To compute energy loss to all orders in opacity we use algebraic recursive method described in (GLV,Nucl.Phys.B594(01)).

  10. Final Result to Arbitrary Order in Opacity (L/l)n MQ and mg > 0 Hard, Gunion-Bertsch, and Cascade ampl. in GLV generalized to finite M Generalizes GLV MQ = mg =0 (Nucl. Phys. B 594, 2001)

  11. The numerical results for induced radiative energy loss are shown for first order in opacity, for L= 5 fm, l=1fm. For 10 GeV heavy quark (c, b) jet, thickness dependence is closer to linear Bethe-Heitler like form L1. This is different than the asymptotic energy quadratic form characteristic for light quarks.

  12. Quantitative “dead cone effect” for the heavy quark energy loss light

  13. RHIC LHC u,d c b As the jet energy increases, the dead cone effect becomes less important.

  14. The numerical results can be understood from: LPM effects are smaller for heavy than for light quarks! 1st order energy loss can not be characterized only by a “Dead-cone” effect! Results confirmed by two independent groups: B. W. Zhang, E. Wang and X. N. Wang, Phys.Rev.Lett.93:072301,2004; N. Armesto, C. A. Salgado, U. A. Wiedemann, Phys.Rev.D69:114003,2004.

  15. Before quenching After quenching Pt distributions of charm and bottom before and after quenching at RHIC M. D., M. Gyulassy and S. Wicks, Phys. Rev. Lett. 94, 112301 (2005); Euro Phys. J C, in press (2005).

  16. Heavy quark suppression as a function of pt Moderate D mesonsuppression ~ 0.50.1at RHIC. (M. D., M. Gyulassy and S. Wicks, Phys. Rev. Lett. 94, 112301 (2005);Euro Phys. J C, press)

  17. Single electrons pt distributions before and after quenching at RHIC Panels show single e- from FONLL(done by R. Vogt).(M. D., M. Gyulassy, R. Vogt and S. Wicks, nucl-th/0507019, to appear Phys. Lett. B (2005)) Before quenching After quenching Bottom dominate the single e-spectrum after 4.5 GeV!

  18. Domination of bottom in single electron spectra The ratio of charm to bottom decays to electrons obtained by varying the quark mass and scale factors. Plot done by Simon Wicks.

  19. At pt~5GeV, RAA(e-) 0.70.1at RHIC. Single electron suppression as a function of pt red curves: be;blue curves: ce; black curves: b+ce;

  20. dNg/dy=1000 Comparison with single electron data Disagreement with PHENIX preliminary data!

  21. dNg/dy=3500 How can we solve the problem? Reasonable agreement, but the dNg/dy=3500 is not physical!

  22. Are there other energy loss mechanisms? Elastic v.s. radiative energy loss: Elastic and radiative energy losses are comparable! (see M. G. Mustafa, Phys.Rev.C72:014905,2005)

  23. Heavy quark suppression with the elastic energy loss Plots done by Simon Wicks. CHARM BOTTOM The elastic energy loss significantly changes the charm and bottom suppression!

  24. Single electron suppression with the elastic energy loss (S. Wicks, W. Horowitz, M.D. and M. Gyulassy, in preparation.) Include elastic energy loss Reasonable agreement with single electron data, even for dNg/dy=1000. Plot done by Simon Wicks. However, overprediction of pion suppression results happens.Solution: Include the geometrical fluctuations (see M. Gyulassy’s talk).

  25. Is the elastic energy loss important at LHC? Elastic v.s. radiative energy loss: Radiative energy loss dominates at high pt!

  26. Conclusions We applied the theory of heavy quark energy loss to compute heavy meson and single electron suppression. We show that bottom quark contribution can not be neglected in the computation of single electron spectra. The recent single electron data show significant discrepancies with theoretical predictions based only on radiative energy loss. However, inclusion of the elastic energy loss may lead to the agreement with experimental results.

  27. Acknowledgements: Miklos Gyulassy (Columbia University) Ramona Vogt (LBNL, Berkeley and University of California, Davis) Simon Wicks (Columbia University)

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