1. Heavy Quark and charm propagation in Quark-Gluon plasma
2009/11/25
Discussion with Prof. Blaizot
Heavy Quark and charm propagation in Quark-Gluon plasma
Yukinao Akamatsu
Tetsuo Hatsuda
Tetsufumi Hirano
(Univ. of Tokyo)
Ref : Y.A., T.Hatsuda and T.Hirano, PRC79, (2009)
Y.A., T.Hatsuda and T.Hirano, PRC80,031901(R) (2009)

2. Outline Introduction Langevin + Hydro Model for Heavy Quark
Numerical Calculations
Conclusions and Outlook
Discussion

3. Medium composed of light particles (u,d,s,g)
Introduction
0.6fm
O(10) fm
initial thermalization hydrodynamics hadron scattering observed
Medium composed of light particles (u,d,s,g)
Strongly coupled QGP (sQGP)  How can we probe it?
Others : jets, J/Psi, etc
Heavy quarks (c,b) --- heavy compared to temperature
tiny thermal pair creation
　　　　　　　　　　　　　　　　　 no mutual interaction
 Good probe !

4. Langevin + Hydro Model for Heavy Quark
1) Our model of HQ in medium
in the (local) rest
frame of matter
Relativistic Langevin equation
Assume isotropic Gaussian white noise
the only input,
dimensionless
Satisfy fluctuation-dissipation
theorem
2) Energy loss of heavy quarks
Weak coupling (pQCD)
(leading order)
Poor convergence
(Caron-Huot ‘08)
Strong coupling (SYM by AdS/CFT  sQGP)
[ for naïve perturbation]
N=4 SYM theory
(Gubser ’06, Herzog et al. ’06, Teaney ’06)
“Translation” to sQGP
(Gubser ‘07)

5. c(b)→D(B)→e- +νe+π etc
3) Heavy Quark Langevin + Hydro Model
0 fm….
Little Bang
generated by PYTHIA
0.6 fm…
Initial Condition
(pp + Glauber)
Local temperature and flow
Brownian Motion
Full 3D hydrodynamics
QGP
T(x), u(x)
(Hirano ’06)
Heavy Quark Spectra _
c(b)→D(B)→e- +νe+π etc
O(10)fm…
(independent fragmentation)
Electron Spectra + ….
Experiment
(PHENIX, STAR ’07)
time

6. Numerical Calculations
1) Nuclear Modification Factor & Elliptic Flow
Experimental result  γ=1-3
(AdS/CFT γ=2.1±0.5)
charm : nearly thermalized
bottom : not thermalized
Different freezeouts at 1st order P.T.
γ=1-3  Much smaller elliptic flow than in experiment
bottom dominant
・Initial (LO pQCD) : good only at high pT
・CNM, quark coalescence : tiny at high pT

7. 2) Azimuthal Correlation
Back to back correlation of a heavy quark pair
diffusion
Loss of correlation in decay products from D & B
e(mid-pseudorapidity)-μ(fwd-pseudorapidity)
correlation : one peak
no contribution from vector meson decay
IAA : quantitative measure
e-μ azimuthal correlation: sensitive probe for heavy quark thermalization rate

8. e-h correlation (mid-pseudorapidity) : two peaks
A sensitive probe but not clean …
Effects we ignore :
・Hadronic interaction of associates
・Medium response to HQ propagation
・Fictitious correlation due to bulk v2
Relative angle range for IAA
Near side : -0.5π≦Δφ≦0.5π
Away side : 0.5π≦Δφ≦1.5π

9. Drag parameter cannot explain RAA and v2 simultaneously.
Conclusions and Outlook
Heavy quark can be described by relativistic Langevin dynamics with a drag parameter predicted by AdS/CFT (for RAA).
Drag parameter cannot explain RAA and v2 simultaneously.
A proposal of electron-muon correlation as a new tool to probe the heavy quark drag parameter.
Possible updates for
initial distribution with FONLL pQCD
quark coalescence, CNM effects,・・・
(but almost done by Dr. Morino)

10. Backup

11. Weak coupling calculations for HQ energy loss
γ~2.5
γ~0.2
RHIC, LHC

12. A Little More on Langevin HQ
Fluctuation-dissipation theorem
Ito discretization  Fokker Planck equation
Generalized FD theorem

13. Notes in our model Initial condition <decayed electron in pp>
<HQ in pp>
available only spectral shape
above pT ~ 3GeV
Reliable at high pT
No nuclear matter effects in initial condition
No quark coalescence effects in hadronization
Where to stop in mixed phase at 1st order P.T.
 3 choices (no/half/full mixed phase)
f0=1.0/0.5/0.0