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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

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
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
slide3

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? )

slide4

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

slide5

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.

slide6

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.

slide8

Phys. Rev. Lett. 98 (2007) 192301

RAA and B/D of non-photonic electrons

p+p 200 GeV

Central 0-5% Au+Au

constraining r aa b and r aa c
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

r aa p t 6gev c almost p t independent
RAA(pT>6GeV/c) Almost pT Independent

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

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

slide11

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?

npart dependence of energy loss

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
Absence of Explicit Path Length Dependence

not used

The centrality dependence of DpT/pTcould be due to

the initial energy density in collisions !

what possible physical scenario for eloss without l dependence

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 !

slide15

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 !

slide16

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
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
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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