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

1)PT Scale for Jet Energy Loss in QCD Medium

2)Non-photonic RAA and Bottom versus Charm

3)Is There a Clear Path-Length Effect in Eloss?

4)Mach Cone Effect for Heavy Quark Jet

5)v2 at High pT

pT Scales and Physical Processes

RCPThree 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

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.

pT_asso > 0.3 GeV/c

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

RAA and B/D of non-photonic electrons

Phys. Rev. Lett. 98 (2007) 192301

Central 0-5% Au+Au

p+p 200 GeV

)1(

)()()(

)/(

rRrRR

ee

e

eN

e

ee

e

eN

e

eeN

eeR

eeer

CAA

BAAAA

ppC

ppB

ppC

ppCbin

AAC

ppC

ppB

ppB

ppBbin

AAB

ppC

ppBbin

AAC

AAB

AA

ppC

ppB

ppB

Constraining RAA(B) and RAA(C)

Theory RangeM.Djordjevic, PLB632, 81 (2006)

LqAA

HQAA

CAA

BAA

RR

RR

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 !!

pT > 5 GeV/c

Energy Loss Shifts pp pT to AA pT-pT

pp

AA/Nbin

pT

For a power-law function (1+pT/a)-n a flat RAA pT/pT constant ! What Physical Processes?

Npart Dependence of Energy Loss

Npart2/3

pT > 5 GeV/c

No significant difference in pT/pT between light hadron and non-photonic electrons !pT/pT ~ 25% in most central collisions !The physical origin of the N2/3 dependence? Linear Npart not bad either

not used

Absence of Explicit Path Length Dependence

The centrality dependence of pT/pTcould be due to the initial energy density in collisions !

not used

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 !

Path-Length Dependence in Soft Particles

3<pTtrig<4GeV/c & 1.0<pT

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 pT region, the medium response to Parton ELoss -- has path-length dependenceCaution: the current trigger pT is high enough to be in the dominant parton energy loss domain !

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.

0 – 20% most central Cu+Cu collisions at 200 GeV :

pTtrig = 3-6 GeV/c; pT

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?

Directi

on re

pres

enta

tionGang Wang (STAR)

ST

AR

Prelim

inary

Uncertainty from ZYAM

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 dependence on parton ELoss on jet-medium interaction Mach cone formation?

SummaryParton 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.