Probing theρspectral function in hot and dense nuclear matter by dileptons

Abstract

We present a dynamical study of e{sup +}e{sup {minus}} and {mu}{sup +}{mu}{sup {minus}} production in proton-nucleus and nucleus-nucleus collisions at CERN-SPS energies on the basis of the covariant transport approach HSD employing a momentum-dependent {rho}-meson spectral function that includes the pion modifications in the nuclear medium as well as the polarization of the {rho} meson due to resonant {rho}-N scattering. We find that the experimental data from the CERES and HELIOS-3 Collaborations can be described equally well as within the dropping {rho}-mass scenario. Whereas corresponding dilepton q{sub T} spectra are found to be very similar, the inclusive dilepton yield in the invariant mass range 0.85{le}M{le}1.0 GeV should allow us to disentangle the two scenarios experimentally. {copyright} {ital 1998} {ital The American Physical Society}