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 1)P T Scale for Jet Energy Loss in QCD Medium 2)Non-photonic R AA and Bottom versus Charm 3)Is There a Clear Path-Length Effect in Eloss? 4)Mach Cone Effect for Heavy Quark Jet 5)v 2 at High p T

3. p T Scales and Physical Processes R CP Three P T 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 R AA -- energy loss of HQ Experimental measurement of B and D contributions to non-photonic electrons ! Direct measurement of D and B mesons

5. PYTHIA B D X.Y. Lin, hep-ph/0602067 B vs D: contribution to non-photonic e 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. p T_asso > 0.3 GeV/c

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 < p T < 9 GeV/c, and FONLL prediction is consistent with our data within errors.

7. Bottom Quarks Suffer Energy Loss Too

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

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

10. R AA (p T >6GeV/c) Almost p T Independent R AA =(Au+Au)/[N binary x(p+p)] Empirical Implications for a constant R AA for p T > 6 GeV/c !!

11. p T > 5 GeV/c Energy Loss Shifts pp p T to AA p T -  p T pp AA/N bin pTpT For a power-law function (1+p T /a) -n a flat R AA   p T /p T constant ! What Physical Processes?

12. Npart Dependence of Energy Loss Npart 2/3 p T > 5 GeV/c No significant difference in  p T /p T between light hadron and non-photonic electrons !  p T /p T ~ 25% in most central collisions ! The physical origin of the N 2/3 dependence? Linear Npart not bad either not used

13. Absence of Explicit Path Length Dependence The centrality dependence of  p T /p T  could be due to the initial energy density in collisions ! not used

14. What Possible Physical Scenario for ELoss without L dependence T. Hirano et al, Phys. Rev. C69, 034908 (2004) 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 3<p T trig <4GeV/c & 1.0<p T asso <1.5GeV/c 20-60% STAR  =  associate -  trigger (rad) Parallel: M. McCumber; O. Catu; H. Pei A. Feng; O. Barannikova; A. Adare At low p T region, the medium response to Parton ELoss -- has path-length dependence Caution: the current trigger p T is high enough to be in the dominant parton energy loss domain !

16. After v 2 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 v 2 subtraction. 0 – 20% most central Cu+Cu collisions at 200 GeV : p T trig = 3-6 GeV/c; p T asso = 0.15-0.5 GeV/c Non-photonic e-h azimuthal correlation trigger Away Side in medium : How does B/D lose energy? Via conical emission? Direction representation Gang Wang (STAR) STAR Preliminary Uncertainty from ZYAM

17. Future Test of Path Length Dependence Precise value of v 2 at p T > 6, 10 GeV/c ? R AA at pT > 10 GeV/c at RHIC should R AA approach unity at higher p T ? Future measurements will shed lights on possible physical scenarios for parton energy loss dynamics ! Heavy Quarks will be special -- Lorentz  dependence on parton ELoss on jet-medium interaction Mach cone formation?

18. Summary Parton Energy Loss  Hadron P T 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 v 2 Measurement at High p T (> 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.