From - and Photon-Nucleon Scattering to Vector Mesons in Nuclear Matter

A covariant and unitary approach to pion- and photon-nucleon scattering taking the πN, ρN, ωN, ηN, πΔ, KΛ and KΣ channels into account is presented. It is argued that the s- and d-wave nucleon N(1535), N(1650), N(1520) and N(1700) resonances and as well as the isobar Δ(1620) and Δ(1700) resonances should be generated in terms of coupled channel dynamics. A fair description of the experimental data relevant for the properties of slow vector-mesons in nuclear matter is obtained. The ρ- and ω-meson spectral functions are evaluated in nuclear matter according to the low-density theorem. They are determined by the vector-meson nucleon scattering amplitudes as obtained in the coupled channel analysis.