Probing properties of the qcd medium via heavy quark induced hadron correlations
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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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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

  • 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


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? )


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


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.


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.


Bottom Quarks Suffer Energy Loss Too


Phys. Rev. Lett. 98 (2007) 192301

RAA and B/D of non-photonic electrons

p+p 200 GeV

Central 0-5% Au+Au


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


RAA(pT>6GeV/c) Almost pT Independent

RAA=(Au+Au)/[Nbinaryx(p+p)]

Empirical Implications for a constant RAA for pT > 6 GeV/c !!


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?


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


Absence of Explicit Path Length Dependence

not used

The centrality dependence of DpT/pTcould be due to

the initial energy density in collisions !


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 !


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 !


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.


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?


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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