RHO-MESON PROPAGATION AND DILEPTON ENHANCEMENT IN HOT HADRONIC MATTER

A realistic model for the free rho meson with coupling to two-pion sta tes is employed to calculate the rho propagator in a hot and dense had ron gas. The medium modifications are based on hadronic rescattering p rocesses: intermediate two-pion states are renormalized through intera ctions with surrounding nucleons and deltas, and rho meson scattering is considered off nucleons, deltas, pions and kaons. Constraints from gauge invariance as well as the full off-shell dynamics of the interac tions are accounted for. Within the vector dominance model we apply th e resulting in-medium rho spectral function to compute e(+)e(-) produc tion rates from pi(+)pi(-) annihilation. The calculation of correspond ing e(+)e(-) spectra as recently measured in central collisions of hea vy-ions at CERN/SpS energies gives reasonable agreement with the exper imental data. (C) 1997 Elsevier Science B.V.