Boson exchange phenomenology: A first step from nucleons to nuclei

Abstract

We investigate medium renormalization effects of strong and weak meson-nucleon vertex functions in the framework of a non-linear chiral meson theory. The density dependence of the nucleon properties is entirely determined by the medium renormalization of the fundamental meson parameters. Our results indicate a mild density dependence of the strong-coupling constants and quenching of the respective form factors. The parity-violating weak meson-nucleon couplings are strongly suppressed in the medium even for moderate density variations of the mesonic parameters like e.g. the pion decay constant or the vector meson masses. We discuss the implications of these results for the boson-exchange phenomenology of strong and weak nuclear forces. We also study the Δ(1232) resonance in the medium. We find that for constant vector meson masses, the NΔ mass splitting M Δ − M N is not shifted from its free space value whereas for decreasing vector meson masses it is quenched by ∼10%. We compare these results to empirical information gained from the study of the nuclear forward Compton amplitude. We also show that the coupling of scalar particles by means of the QCD trace anomaly does not affect the medium renormalization of the nucleon properties.