Thermal photon production in high-energy nuclear collisions.

We use a boost-invariant one-dimensional (cylindrically symmetric) fluid dynamics code to calculate thermal photon production in the central rapidity region of S+Au and Pb+Pb collisions at SPS energy ( √ s = 20 GeV/nucleon). We assume that the hot matter is in thermal equilibrium throughout the expansion, but consider deviations from chemical equilibrium in the high temperature (deconfined) phase. We use equations of state with a first-order phase transition between a massless pion gas and quark gluon plasma, with transition temperatures in the range 150 ≤ Tc ≤ 200 MeV. Typeset using REVTEX Electronic mail (internet): [email protected]. Current address: Department of Physics, McGill University, 3600 University St., Montreal, QC, H3A 2T8, Canada. Electronic mail (internet): [email protected]. Electronic mail (internet): [email protected]. 1