Dilepton production and mT-scaling at BEVALAC/SIS energies

We present a dynamical study of e(+)e(-) production in C+C and Ca+Ca collisions at BEVALAC/SIS energies on the basis of the covariant transport approach HSD employing momentum-dependent rho-meson spectral functions that include 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 DLS Collaboration cannot be described within the rho-meson spectral Function approach. A dropping eta-mass scenario leads to a good reproduction of the DLS dilepton data, however, violates the m(T)-scaling of pi(0) and eta spectra as observed by the TAPS Collaboration as well as eta photoproduction on nuclei. (C) 1998 Elsevier Science B.V.