A Second Look at Single Photon Production in S+Au Collisions at 200 A⋅\cdotGeV and Implications for Quark Hadron Phase Transition

We reanalyze the production of single photons in S+Au collisions at CERN SPS to investigate: i) the consequences of using a much richer equation of state for hadrons than the one used in an earlier study by us; and, ii) to see if the recent estimates of photon production in quark-matter (at two loop level) by Aurenche et al. are consistent with the upper limit of the photon production measured by the WA80 experiment. We find that the measured upper limit is consistent with a quark hadron phase transition. The measured upper limit is also consistent with a scenario where no phase transition takes place, but where the hadronic matter reaches a density of several hadrons per unit volume; which is rather unphysical.Comment: 10 pages, including 3 figures; Submitted to Euro. Phys. Jour.

Direct photon production from viscous QGP

We simulate direct photon production in evolution of viscous QGP medium. Photons from Compton and annihilation processes are considered. Viscous effect on photon production is very strong and reliable simulation is possible only in a limited $p_T$ range. For minimally viscous fluid $\eta/s$=0.08), direct photons can be reliably computed only up to $p_T \leq$ 1.3 GeV. With reduced viscosity ($\eta/s$=0.04), the limit increases to $p_T \leq$2GeV.Comment: 6 pages, 5 figure

Spectral Red-Shift Versus Broadening from Photon and Dilepton Spectra

We estimate the photon and dilepton emission rates from hot hadronic matter with in-medium spectral shift and broadening of vector mesons. It is observed that both the WA98 photon data and CERES/NA45 dilepton data can be well reproduced with similar initial conditions. The freeze-out condition has been constrained by the transverse mass spectra of pions and protons measured by the NA49 collaboration. We argue that simultaneous measurement of the $p_T$ spectra of single photons as well as invariant mass distribution of dileptons is crucial to understand the in-medium spectral function of the vector mesons.Comment: Title and contents change