ρ→ππ decay in nuclear medium Original Research Article

We calculate the medium modifications of the ρππ vertex in a relativistic hadronic framework incorporating nucleons and Δ(1232) isobars, and find a substantial increase of the ρππ coupling, dominated by processes where the Δ is excited. The coupling depends significantly on the virtuality of the ρ, which is related to analytic properties of the vertex function. We analyze the general case of a nonzero three-momentum of the ρ with respect to the nuclear medium, and evaluate the resulting widths and spectral strength in the transverse and longitudinal channels for the ρ→ππ decay. These widths are used to obtain the dilepton yields from ρ decays in relativistic heavy-ion collisions.