Nuclear
Physics Colloquium
Location:
Institute for Theoretical Physics, Physics Building, Seminar Room PHYS
2.116
Time: Thursday, October 23, 4:00-5:00pm
(s.t.) (plus
10min for discussion)
Contact: hees@fias.uni-frankfurt.de
How the semi-QGP
may help resolve the puzzle of the large elliptic flow for photons in
AA collisions
Robert Pisarski
(Brookhaven National Laboratory)
We
consider the thermal production of dileptons and photons above the
critical temperature in QCD. In the semi-Quark Gluon Plasma
(QGP), color excitations are suppressed by a small value of the
Polyakov loop. Comparing the semi-QGP to the usual, perturbative
QGP, we find a mild enhancement of thermal dileptons. In
contrast, to leading logarithmic order in weak coupling there are far
fewer hard photons from the semi-QGP than the usual QGP. To
illustrate the possible effects we use a hydrodynamic model.
Dileptons uniformly exhibit a small flow, but the strong suppression
of photons in the semi-QGP tends to bias the elliptical flow of
photons to that generated in the hadronic phase.
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