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Heavy Quark Energy Loss

Heavy Quark Energy Loss. William Horowitz Columbia University June 6, 2006. With many thanks to Simon Wicks, Azfar Adil, Miklos Gyulassy, Magdalena Djordjevic, and Brian Cole. Azfar Adil. Simon Wicks. Glue and Lights. Charm and Bottom. R AA ( j )=R AA (1+2v 2 Cos(2 j )+…).

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Heavy Quark Energy Loss

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  1. Heavy Quark Energy Loss William Horowitz Columbia University June 6, 2006 With many thanks to Simon Wicks, Azfar Adil, Miklos Gyulassy, Magdalena Djordjevic, and Brian Cole Azfar Adil Simon Wicks RHIC & AGS Annual Users’ Meeting ‘06

  2. Glue and Lights Charm and Bottom RAA(j)=RAA(1+2v2Cos(2j)+…) • Correlations of back-to-back jets, etc. RHIC & AGS Annual Users’ Meeting ‘06

  3. Jets as a Tomographic Probe Probe the unknown rQGP with energy loss • Tomography requires precision measurements AND precision, pQCD theory Quark or Glue Jet probes: (h, pT, j - jreac, MQ) init Hadron jet fragments: (h, pT, j – jreac ) final RHIC & AGS Annual Users’ Meeting ‘06

  4. Jets as a Tomographic Probe (cont’d) • If pQCD makes the correct predictions, we can use to understand the medium • Otherwise, jet suppression is just another non-perturbative anomaly of A+A collisions (like J/Y suppression) RHIC & AGS Annual Users’ Meeting ‘06

  5. Before the e- RAA, the picture looked pretty good: • Null Control: RAA(g)~1 Y. Akiba for the PHENIX collaboration, hep-ex/0510008 • Consistency: RAA(h)~RAA(p) • GLV Prediction: Theory~Data for reasonable fixed L~5 fm and dNg/dy~dNp/dy RHIC & AGS Annual Users’ Meeting ‘06

  6. Theory v2 too small Fragile Probe? But with Hints of Trouble: A. Drees, H. Feng, and J. Jia, Phys. Rev. C71:034909 (2005) (first by E. Shuryak, Phys. Rev. C66:027902 (2002)) K. J. Eskola, H. Honkanen, C. A. Salgado, and U. A. Wiedemann, Nucl. Phys. A747:511:529 (2005) RHIC & AGS Annual Users’ Meeting ‘06

  7. What Can Heavies Teach Us? • Provide a unique test of our understanding of energy loss • Mass => Dead Cone => Reduction in E loss = Bottom Quark • (Gratuitous Pop Culture Reference) RHIC & AGS Annual Users’ Meeting ‘06

  8. Entropy-constrained radiative-dominated loss FALSIFIED by e- RAA Problem: Qualitatively, p0 RAA~ e- RAA RHIC & AGS Annual Users’ Meeting ‘06

  9. Inherent Uncertainties in Production Spectra How large is bottom’s role? M. Djordjevic, M. Gyulassy, R. Vogt, S. Wicks, Phys. Lett. B632:81-86 (2006) • Vertex detectors could de-convolute the e- contributions N. Armesto, M. Cacciari, A. Dainese, C. A. Salgado, U. A. Wiedemann, hep-ph-0511257 RHIC & AGS Annual Users’ Meeting ‘06

  10. The BDMPS-Z-WS Approach • Increase to 14 to push curve down • Fragility in the model allows for consistency with pions N. Armesto, M. Cacciari, A. Dainese, C. A. Salgado, U. A. Wiedemann, hep-ph-0511257 RHIC & AGS Annual Users’ Meeting ‘06

  11. What Does Mean? We believe it’s nonperturbative: • a = .5 => dNg/dy ~ 13,000 “Proportionality constant ~ 4-5 times larger than perturbative estimate” K. J. Eskola, H. Honkanen, C. A. Salgado, and U. A. Wiedemann, Nucl. Phys. A747:511:529 (2005) “Large numerical value of not yet understood” R. Baier, Nucl. Phys. A715:209-218 (2003) U. A. Wiedemann, SQM 2006 RHIC & AGS Annual Users’ Meeting ‘06

  12. Is this Plausible? Maybe • Flow nonperturbative at low-pT • v2 possibly nonperturbative at mid-pT • Asymptotic Freedom MUST occur • But at what momentum? WH, nucl-th/0511052 D. Winter, QM2005 RHIC & AGS Annual Users’ Meeting ‘06

  13. But what if we Neglected an Important Effect? M. Mustafa, Phys. Rev. C72:014905 (2005) S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076 RHIC & AGS Annual Users’ Meeting ‘06

  14. Elastic History People have thought about Elastic Loss for a long time, and in different ways—all assume parton starts in asymptotic past • J. D. Bjorken, FERMILAB-PUB-82-059-THY (Quantal) • M. H. Thoma and M. Gyulassy, Nucl. Phys. B351:491-506 (1991) (Classical) • E. Braaten and M. H. Thoma, Phys. Rev. D24:2625-2630 (1991) (Quantal) • P. Romatschke and M. Strickland, Phys. Rev. D71:125008 (2005) (Quantal) Bottom Charm Most correct (infinite time) elastic loss calculation approximately bounded by BT and TG curves RHIC & AGS Annual Users’ Meeting ‘06

  15. Include Path Length Fluctuations with Realistic Geometry • For fixed L~5 fm, Collisional+Radiative leads to pion overquenching • Use Woods-Saxon density • hard production ~ TAA • medium ~ rparticipant • This allows a self- consistent pion prediction without “fixed L”approx S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076 RHIC & AGS Annual Users’ Meeting ‘06

  16. Our Extended Theory • Convolve Elastic with Inelastic energy loss fluctuations • Include path length fluctuations in diffuse nuclear geometry • Separate calculations with BT and TG collisional formulae provide a measure of the elastic theoretical uncertainty RHIC & AGS Annual Users’ Meeting ‘06

  17. Conservative Results • Elastic loss improves quench • keeping • dNg/dy = 1000 • as = .3 • and No change in c or b production cross sections • Extended Theory is consistent with data for pT > 7 GeV S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076 RHIC & AGS Annual Users’ Meeting ‘06

  18. Consistency Test with Pions Not flat, which requires a balance of many competing effects (Cronin, EMC, etc.) but not at odds with data S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076 RHIC & AGS Annual Users’ Meeting ‘06

  19. El+Rad+Geom NOT a Fragile Probe • Why? First, experimental error bars have shrunk considerably since 2004. Second, sDE,el < sDE,rad WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation RHIC & AGS Annual Users’ Meeting ‘06

  20. Why Widths are Vital • The whole distribution is important: , but sDE,el < sDE,rad S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076 RHIC & AGS Annual Users’ Meeting ‘06

  21. Elastic Objections • All derivations start parton at asymptotic past: are there formation time effects? • Peigne et al. (Classical): • This is unintuitive: one expects effects to disappear by L ~ 1/mD ~ .5 fm, the screening scale; but perhaps there is a hidden g factor • What about interference effects? They claim NO elastic loss until L > 10 fm! S. Peigne, P.-B. Gossiaux, and T. Gousset, JHEP0604:011 (2006) RHIC & AGS Annual Users’ Meeting ‘06

  22. Adil et al. Classical Refutation of Peigne et al. Two issues: • Peigne et al. do not disentangle known radiative effects • small • Peigne et al. neglect a term in their classical current, thereby violating current conservation and resulting in a spurious A. Adil, M. Gyulassy, WH, and S. Wicks, nucl-th/0606010 • subtraction of the (negative) binding energy of the quark-antiquark pair • HUGE RHIC & AGS Annual Users’ Meeting ‘06

  23. Classical Finite Time Results By L ~ 1/mD, stable field reaches ~ 90% of the asymptotic 10 GeV Charm 10 GeV Charm A. Adil, M. Gyulassy, WH, and S. Wicks, nucl-th/0606010 RHIC & AGS Annual Users’ Meeting ‘06

  24. Quantal Finite Time Results Again, formation effects negligible beyond 1/mD M. Djordjevic, nucl-th/0603066 X. N. Wang, nucl-th/0604040 No one as yet fully combines El+Rad with interference RHIC & AGS Annual Users’ Meeting ‘06

  25. Heavy Quark Tomography of the LHC • Additional systematic tests of the energy loss theory • 2-3 times RHIC medium densities • Enormous pT range • At very high momenta, GLV and BDMPS-Z-WS results converge, but elastic effects persist! WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation RHIC & AGS Annual Users’ Meeting ‘06

  26. LHC Predictions WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation RHIC & AGS Annual Users’ Meeting ‘06

  27. Conclusions • Fantastic new RHIC data challenging, surprising • Better understanding of heavy quark loss mechanisms, production critical for interpreting experimental results • Large uncertainties in ratio of charm to bottom contribution to non-photonic electrons • Direct measurement of D spectra would help separate the different charm and bottom jet dynamics • FONNLL would provide better information on theoretical production error RHIC & AGS Annual Users’ Meeting ‘06

  28. Conclusions (cont’d) • BDMPS-Z-WS: • IF extreme is assumed • IF elastic loss is assumed to vanish • IF they assume fragility • Then not inconsistent with data • No hope for tomography RHIC & AGS Annual Users’ Meeting ‘06

  29. Conclusions (cont’d) • DGLV: • Include elastic, inelastic, and path length fluctuations • Consistent results for high-pTe- RAA • Pion RAA predictions agree well with data over large momentum range, are sensitive to changes in medium density, consistent with multiplicity constraints RHIC & AGS Annual Users’ Meeting ‘06

  30. Conclusions (cont’d) • Far from finished: • Coherence and correlation effects between elastic and inelastic processes that occur in a finite time over multiple collisions must be sorted out • Fixed a must be allowed to run; the size of the irreducible error due to integration over low, nonperturbative momenta, where a > .5, needs to be determined • Where will e- RAA data and theoretical calculations settle down as research progresses and error bars are reduced over time? RHIC & AGS Annual Users’ Meeting ‘06

  31. Conclusions (cont’d) P. Arnold, G.D. Moore, and L. Yaffe, JHEP 011:057 (2001) S. Turbide, C. Gale, S. Jeon, G. D. Moore, Phys. Rev. C72:014906 (2005) • AMY: a third approach? • Produced a pion RAA; no calculation of e- RAA, a crucial consistency check • The LHC will provide an excellent new testing ground for systematic study (falsification?) of energy loss theory • Jet tomography is an elusive, but achievable goal RHIC & AGS Annual Users’ Meeting ‘06

  32. RHIC & AGS Annual Users’ Meeting ‘06

  33. Backup Slides RHIC & AGS Annual Users’ Meeting ‘06

  34. WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation RHIC & AGS Annual Users’ Meeting ‘06

  35. S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076 RHIC & AGS Annual Users’ Meeting ‘06

  36. WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation RHIC & AGS Annual Users’ Meeting ‘06

  37. WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation RHIC & AGS Annual Users’ Meeting ‘06

  38. WH, S. Wicks, M. Gyulassy, M. Djordjevic, in preparation RHIC & AGS Annual Users’ Meeting ‘06

  39. K. J. Eskola, H. Honkanen, C. A. Salgado, and U. A. Wiedemann, Nucl. Phys. A747:511:529 (2005) A. Dainese, C. Loizides, G. Paic, Eur. Phys. J. C38:461-474 (2005) RHIC & AGS Annual Users’ Meeting ‘06

  40. N. Armesto, M. Cacciari, A. Dainese, C. A. Salgado, U. A. Wiedemann, hep-ph-0511257 A. Dainese, C. Loizides, G. Paic, Eur. Phys. J. C38:461-474 (2005) RHIC & AGS Annual Users’ Meeting ‘06

  41. A. Dainese, C. Loizides, G. Paic, Eur. Phys. J. C38:461-474 (2005) RHIC & AGS Annual Users’ Meeting ‘06

  42. S. Wicks, WH, M. Gyulassy, and M. Djordjevic, nucl-th/0512076 RHIC & AGS Annual Users’ Meeting ‘06

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