Probing Properties of the QCD Medium via Heavy Quark Induced Hadron Correlations Huan Zhong Huang...
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Transcript of Probing Properties of the QCD Medium via Heavy Quark Induced Hadron Correlations Huan Zhong Huang...
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.
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.