un 1 99 8 ρ - meson properties at finite nuclear density ∗

We calculate the momentum dependence of the ρ-meson selfenergy based on the dispersion relation for the ρN scattering amplitude f(ω) at low nuclear density. The imaginary part of f(ω) is determined from the optical theorem, while the total ρN cross section is obtained within the VDM at high energy and within the resonance model at low energy. Our numerical results indicate a sizeable broadening of the ρ-meson width in the medium especially for low relative momenta p while the real part of the ρ selfenergy is found to change its sign and to become repulsive already at momenta above 100 MeV/c. Extrapolating to nuclear saturation density ρ0 we find a dropping of the ρ-mass for p ≈ 0 roughly in line with the QCD sumrule analysis of Hatsuda while at high energy an increase of the ρ-mass close to the prediction by Eletsky and Joffe is obtained. However, when including a broadening of the baryonic resonances in the medium, the ρmeson mass shift at p ≈ 0 becomes slightly repulsive whereas the width increases substantially. PACS: 25.20.-x; 25.20.Dc; 25.40Ep