PROBING THE RHO-SPECTRAL-FUNCTION IN HOT AND DENSE NUCLEAR-MATTER BY DILEPTONS

We present a dynamical study e(+)e(-) and mu(+)mu(-) production in pro ton-nucleus and nucleus-nucleus collisions at CERN-SPS energies on the basis of the covariant transport approach HSD employing a momentum-de pendent rho-meson spectral function that includes the pion modificatio ns ill tilt nuclear medium as well as the polarization of the rho meso n due to resonant rho-N scattering. We find that the experimental data from tile CERES and HELIOS-3 Collaborations can be described equally well as within tile dropping rho-mass scenario. Whereas corresponding dilepton q(T) spectra are found to be very similar, the inclusive dile pton yield in the invariant mass range 0.85 less than or equal to M le ss than or equal to 1.0 GeV should allow us to disentangle the two sce narios experimentally.