RHO-MESON PROPERTIES AT FINITE NUCLEAR DENSITY

We calculate the momentum dependence of the rho-meson self-energy base d on the dispersion relation for the rho N scattering amplitude f(omeg a) at low nuclear density. The imaginary part of f(w) is determined fr om the optical theorem, while the total rho N cross section is obtaine d within the vector dominance model at high energy and within the reso nance model at low energy. Our numerical results indicate a sizable br oadening of the rho-meson width in the medium especially for low relat ive momenta p while the real part of the rho self-energy is found to c hange its sign and to become repulsive already at momenta above 100 Me V/c. Extrapolating to nuclear saturation density rho(0) we find a drop ping of the rho mass for p approximate to 0 roughly in line with the Q CD sum rule analysis of Hatsuda while at high energy an increase of th e rho mass close to the prediction by Eletsky and Ioffe is obtained. H owever, when including a broadening of the baryonic resonances in the medium, the rho-meson mass shift at p approximate to 0 becomes slightl y repulsive, whereas the width increases substantially.