Role of nucleons in electromagnetic emission rates - art. no. 037502.

Electromagnetic emission rates from a thermalized hadronic gas are importan t for the interpretation of dilepton signals from heavy-ion collisions. Alt hough there is a consensus in the literature about rates for a pure meson g as, qualitative differences appear with a finite baryon density. We show th is to be essentially due to the way in which the pi N background is treated in regards to the nucleon resonances. Using a background constrained by un itarity and broken chiral symmetry, it is emphasized that the thermalized h adronic gas can be considered dilute. [S0556-2821(99)02713-7].