Medium effects on meson couplings and dilepton spectra

The pi omega rho coupling constant is calculated in a relativistic hadronic framework incorporating nucleons and Delta(1232) isobars. Medium modifications are included. The vertex is analyzed in context of the omega to pi e+e- and rho to pi e+e- Dalitz decays in nuclear matter. A sizeable increase of the widths for these decays is found for invariant mass of dileptons in the range 0.2-0.5 GeV. This increase may help, among other medium effects, to explain the problem of the low-mass dilepton enhancement seen in relativistic heavy-ion collisions.