Effect of viscosity on one dimensional hydrodynamic flow and direct photons from 200 AGeV S+Au collisions at CERN SPS

We have analyzed the direct photon data obtained by the WA80 collaboration in 200 A GeV S+Au collision at CERN SPS, in a one dimensional hydrodynamica l model. Two scenarios were considered: (i) formation of quark-gluon plasma and (ii) formation of hot hadronic gas. For both the scenarios, ideal as w ell as extremely viscous fluid was considered. It was found that direct pho ton yield from QGP is not affected much whether the fluid is treated as ide al or extremely viscous. The yield however differ substantially if hadron g as is produced. None of the scenarios gives satisfactory description of the data.