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Probing Properties of the QCD Medium via Heavy Quark Induced Hadron Correlations

Probing Properties of the QCD Medium via Heavy Quark Induced Hadron Correlations. Huan Zhong Huang Department of Physics and Astronomy University of California Los Angeles, CA 90095-1547 June 26-28, 2008: 417. WE-Heraeus-Seminar. Thanks to Gang Wang and Shingo Sakai. Outline.

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Probing Properties of the QCD Medium via Heavy Quark Induced Hadron Correlations

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  1. Probing Properties of the QCD Medium via Heavy Quark Induced Hadron Correlations Huan Zhong Huang Department of Physics and Astronomy University of California Los Angeles, CA 90095-1547 June 26-28, 2008: 417. WE-Heraeus-Seminar Thanks to Gang Wang and Shingo Sakai

  2. Outline • PT Scale for Jet Energy Loss in QCD Medium • Non-photonic RAA and Bottom versus Charm • Is There a Clear Path-Length Effect in Eloss? • Mach Cone Effect for Heavy Quark Jet • v2 at High pT

  3. pT Scales and Physical Processes RCP Three PT Regions: -- Fragmentation -- multi-parton dynamics (recombination or coalescence or …) -- Hydrodynamics (constituent quarks ? parton dynamics from gluons to constituent quarks? )

  4. B and D contributions to electrons Non-photonic e RAA -- energy loss of HQ Experimental measurement of B and D contributions to non-photonic electrons ! Direct measurement of D and B mesons

  5. PYTHIA X.Y. Lin, hep-ph/0602067 B D B vs D: contribution to non-photonic e pT_asso > 0.3 GeV/c PYTHIA shows significant differences in B&D on the near-side correlations in p+p collisions, and we can fit the experimental data to obtain B/D contribution.

  6. B contribution to non-photonic e in p+p 200GeV Almost half-half B and D contributions to non-photonic e’s at 6 < pT < 9 GeV/c, and FONLL prediction is consistent with our data within errors.

  7. Bottom Quarks Suffer Energy Loss Too

  8. Phys. Rev. Lett. 98 (2007) 192301 RAA and B/D of non-photonic electrons p+p 200 GeV Central 0-5% Au+Au

  9. Constraining RAA(B) and RAA(C) Theory Range M.Djordjevic, PLB632, 81 (2006) Prejudice or Reasonable expectation? Need to measure B/D in A+A collisions to determine RAA for B and C quarks! Heavy Flavor Trackers J. Thomas Talk

  10. RAA(pT>6GeV/c) Almost pT Independent RAA=(Au+Au)/[Nbinaryx(p+p)] Empirical Implications for a constant RAA for pT > 6 GeV/c !!

  11. Energy Loss Shifts pp pT to AA pT-DpT pp AA/Nbin DpT pT > 5 GeV/c For a power-law function (1+pT/a)-n a flat RAA DpT/pT constant ! What Physical Processes?

  12. pT > 5 GeV/c Npart2/3 Npart Dependence of Energy Loss not used No significant difference in DpT/pT between light hadron and non-photonic electrons ! DpT/pT ~ 25% in most central collisions ! The physical origin of the N2/3 dependence? Linear Npart not bad either

  13. Absence of Explicit Path Length Dependence not used The centrality dependence of DpT/pTcould be due to the initial energy density in collisions !

  14. T. Hirano et al, Phys. Rev. C69, 034908 (2004) What Possible Physical Scenario for ELoss without L dependence ELoss of Partons: 1) Strong dependence on energy density 2) Rapid decrease of energy density in time interval < traversing time Hydrodynamic models show such a scenario plausible !

  15. Path-Length Dependence in Soft Particles STAR 3<pTtrig<4GeV/c & 1.0<pTasso<1.5GeV/c 20-60%  = associate - trigger (rad) Parallel: M. McCumber; O. Catu; H. Pei A. Feng; O. Barannikova; A. Adare At low pT region, the medium response to Parton ELoss -- has path-length dependence Caution: the current trigger pT is high enough to be in the dominant parton energy loss domain !

  16. Non-photonic e-h azimuthal correlation trigger Uncertainty from ZYAM 0 – 20% most central Cu+Cu collisions at 200 GeV : pTtrig= 3-6 GeV/c; pTasso = 0.15-0.5 GeV/c Gang Wang (STAR) Direction representation STAR Preliminary Away Side in medium: How does B/D lose energy? Via conical emission? After v2 subtraction, the double-hump has a significance of 3~4 sigma. PYTHIA fit has a big chi2. On the away side, a broad structure or a possible double-hump feature has been observed, even before v2 subtraction.

  17. Future Test of Path Length Dependence Precise value of v2 at pT > 6, 10 GeV/c ? RAA at pT > 10 GeV/c at RHIC should RAA approach unity at higher pT ? Future measurements will shed lights on possible physical scenarios for parton energy loss dynamics ! Heavy Quarks will be special -- Lorentz g dependence on parton ELoss on jet-medium interaction Mach cone formation?

  18. Summary Parton Energy Loss  Hadron PT Scale > 5-6 GeV/c Heavy Quarks (Charm/Bottom) Suffer Energy Loss -- Need Direct Charm/Bottom Measurement in A+A Absence of Clear Path-Length Dependence of ELoss -- Rapid Decrease of Energy Density with Evolution Time -- Need v2 Measurement at High pT (> 6 GeV/c) Jet-medium Interaction Induces Correlations in the Soft Particle Regime – Path-Length Dependent Possibly for Conic Shape Correlation Even for Heavy Quark Induced Jet-Medium Int.

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