Photoproduction of vector mesons off nucleons near threshold

Abstract

We propose a simple meson-exchange model of the photoproduction of $ρ$- and $ω$-mesons off protons near threshold ($E_γ$ less than 2 GeV). This model provides a good description of the available data and implies a large $ρ$-nucleon interaction in the scalar channel ($σ$-exchange). We use this phenomenological interaction to estimate the leading contribution to the self-energy of $ρ$-mesons in matter. The implications of our calculation for experimental studies of the $ρ$-meson mass in nuclei are discussed.