Technical concepts are presented that improve the selfconsistent treatment of vector-mesons in a hot and dense medium. First applications concern an interacting gas of pions and rho mesons. As an extension of earlier studies we thereby include RPA-ty
pe vertex corrections and further use dispersion relations in order to calculate the real part of the vector-meson selfenergy. An improved projection method preserves the four transversality of the vector-meson polarisation tensor throughout the selfconsistent calculations, thereby keeping the scheme void of kinematical singularities.
We compute dilepton invariant mass spectra from the decays of rho mesons produced by photon reactions off nuclei. Our calculations employ a realistic model for the rho photoproduction amplitude on the nucleon which provides fair agreement with measur
ed cross sections. Medium effects are implemented via an earlier constructed rho propagator based on hadronic many-body theory. At incoming photon energies of 1.5 -3 GeV as used by the CLAS experiment at JLAB, the average density probed for iron targets is estimated at about half saturation density. At the pertinent rho-meson 3-momenta the predicted medium effects on the rho propagator are rather moderate. The resulting dilepton spectra approximately agree with recent CLAS data.
