Electron-positron pairs from thermal resonances in ultrarelativistic nuclear collisions

We use a boost-invariant one-dimensional (cylindrically symmetric) fluid dynamics code to calculate {ital e}{sup +}{ital e}{sup {minus}} production from {rho}{sup 0} and {omega} decay in the central rapidity region of a central S+Au collision at {radical}{ital s}=20 GeV/nucleon. 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{endash}200 MeV. The production cross section at the {rho} mass loosely constrains the transition and freeze-out temperatures, and we find that the {ital m}{sub {ital T}} spectrum is a good thermometer for sufficiently high {ital T}{sub {ital c}}. {copyright} {ital 1996 The American Physical Society.}