Photo-emission from sQGP

Sang-Jin Sin (Hanyang univ.)

@kitpc, Beijing, 2010/10/22

Based on K.Jo + SJS arXiv:1005.0200

X.Ge, M. Matsuo, F.Shu,T.Tsukioka, sjs arXiv:0806.4460 

Two main difficulties in Nuclear Physics

* Coupling is large. Hard to do reliable calculation * Many particle system difficulty even at lattice QCD

* Need New idea

•AdS/QCD : gives mean field theory that does not require loop calcuation.

The stonger the better.

•Penalty: it is Holographic (5d)

Originally N=4 SUSY

For the strong coupling problem, the ans. is the Gauge/Gravity Duality

Consequences of duality

•Gluon dynamics is replaced by ads gravity.

•Exact Correlation functioncan be calculated by the classical eq. (but in 5d curved space).

• Transports (more later), Phase transition(SC,CSB)

Relativistic Heavy Ion Collider

• Au-Au collision

• E~200 GeV/nucleon

• Seek quark-gluon plasma(QGP)

1010.10.22

Early interests: 4 puzzles

•Perfect fluid : (0806.4460 , 0901.0610 )

•Jet quenching (hep-th/0607123)

•elliptic flow (hep-th/0610113) *

•Early thermalization (hep-th/0511199 )

• These are puzzles from the aspect of AF

but clues to use AdS/CFT.

phenomena-(my contributions)

Usefulness of ads/cft: understanding Perfect

fluidity

Bks

4

/s 0.1h/kB

While perturbative evaluation ~1/g^4

Exp:

ads/cft : Universal value

What about LHC?•Is the medium still strongly interacting ?

If mass production mechanism is too efficient, increasing initial energy does not help to increase the Temp. much.

•For Hadron sprectrum, we expect it is the same as the RHIC since they reprent the moment of the freezout.

Photon & Lepton•On the other hand

photons and leptons can expose the early stage of the fireball.

Photoemission spectral functions are interesting. Strong v.s Weak are very different. (Huot et.al, hepth/0607237).

•No density effect of the medium.

In this talk•Dense matter effect in Photoemission

rate based on the work with KwangHyun Jo.(my student)

•Claim: density effect is yet another interesting effect: LPM and beyond.

•Understand why such dramatic change happens.

Photoemission rate and duality Huot et.al hepth/0607237

Photo prod. in weak g

•Sum of 2-2, Bremstrahlung,pair annihilation

LPM effect yet to be corrected

Lepton production

SYM v.s QCD in weak g Huot et.al hepth/0607237

Zero density resultHuot et.al hepth/0607237

Finite densityK.Jo + SJS arXiv:1005.0200 

density effect in spectral function

To understand Why,

Look Hydro dynamic analysis, which gives the analytic result for the spectral function for small w and k.

In hqcd •Finite temperature quark-gluon

plasma Black hole

•Dense matter Charged black hole

•we use RN balck hole. (for the relevance to the baryonic system, see [arXiv:0707.2719 (sjs)]Bulk filling brane idea.

AdS R-N black hole

Solution to the eq. of M:

Match: BH QGP

Temperature, entropy, energy

pressure, charge density and chemical pot.

Perturbations around RN

perturbed Eintein eq. & Maxwell eq.

X.Ge, Y.Matsuo, F.Shu, SJS,Takuya Tsukioka , arXiv:0806.4460

perturbed Maxwell eq.

Gauge choice and Fourier mode

Classification of modes(for graviton)

Vector type pert and mode mixing.

Infalling BC at horizon Causal Gr.F

perturbative solution near boundary

Hydrodynamic

Mixing effect: Correlation functions in hydro

limittransverse v.s longitudinal

Remark•In the absence of charge,

particle current is NOT diffusive (a=0 or T=0)while heat current is !

Summary of hydro

Result: Density causes Mode Mixing,which establishes diffusion pole.

We expect that it enhences spectral function of photon at low frequency.

Density effect in photo emmision

LPM(Landau-Pomeranchuk-Migdal)Suppression of Brehmstrahlung due

to the density effect. (B is not point like process)

Q: Is it encoded here? We think so. Decrease in the peak at low density.

Notice: after certain critical density, photoemission increases.

Some details for spectral function calculation

for vector mode

Effective action4

In falling BC at horizon: D=0,C=1

relevant caseintroduce

density effect in spectral function (again)

Ac and DC Conductivities

Density effect in spectral function

Remember:The hydro peak is absent if density is 0.

Conclusion

•String theory may be useful for the New experiment.

•Photoemssion spectral curve is Analogy of CMBR curve in cosmology

• LPM effect is counted and different high density effect is predicted.