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 function
can 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
B
k
s
4
/
s
0
.
1
h
/
k
B
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 result
Huot
et.al
hepth
/0607237
Finite density
K.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
T
emperature
, 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 limit
transverse
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 case
introduce
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.
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