Seminar in Hadronic Physics

Covariant and self consistent vertex corrections for pions and isobars in nuclear matter

Felix Riek

Texas A-M

We evaluate the pion and isobar propagators in cold nuclear matter self consistently applying a covariant form of the isobar-hole model. Migdal's vertex correction effects are considered systematically in the absence of phenomenological soft form factors. It is shown that the short-range dressing of the π N Δ vertex has a significant effect on the pion and isobar properties. We study photoproduction off nuclei in order to obtain constrains on the parameters of the model. Using such realistic parameters sets we predict a downward shift of about 50 MeV for the Delta resonance at nuclear saturation density.