Supercooling and final-state effects on dilepton spectra

We consider two problems associated with the production of dileptons during collisions between heavy nuclei at the Brookhaven Relativistic Heavy Ion Collider energy. One is the difference in dilepton yield between an idealized Maxwell construction of phase coexistence and a dynamical phase transition with finite nucleation and phase conversion rates. The other is the contribution from dilepton-producing reactions involving free-streaming hadrons in the final state. We find that the mass spectrum in the range 2mπ<M<2 GeV is dominated by the mixed phase and the final hadron phase, is somewhat sensitive to the degree of supercooling, but is remarkably insensitive to the "freeze-out" temperature which delineates the passage from local thermal equilibrium to free streaming.