Probing vector meson properties in nuclei with photo-production of the neutral pion

The nuclear contribution to forward angle photo-production of the π0-meson is calculated using an effective lagrangian derived from the triangle anomaly. This lagrangian mediates the interaction of a pion, a photon, and a vector meson mean field. The vector meson mass, mv, and the pion decay constant, fπ, are assumed to have a density-dependence given by mv*(r)/mv=fπ*(r)/fπ=1-λ(ρ(r)/ρNM). The nuclear and Coulomb contributions to pion photo-production yield a cross-section which is sensitive to the properties of the vector meson in nuclear matter. In particular, both the overall strength of the vector meson mean field which is parameterized by gv and the density-dependence of the meson field which is parameterized by λ can be extracted. (orig.)