Interactions of ω mesons in nuclear matter and with nuclei

In-medium interactions of omega-mesons in infinitenu clear matter and finite nuclei are investigated in a micro-scopic approach, focused on the particle-hole excitations of the medium involving nucleonic NN-1 and N*N-;(-1) modes, where N* denotes a nucleon resonance. The nuclear polarization tensors include relativistic mean-field dynamics by self-consistent scalar and vector fields. The resulting self-energiesare transmitted to finite nuclei in local density approximation. Real and imaginary parts of longitudinal and transversal self-energies are discussed. The relation of the present approach to meson cloud models is addressed and an ambiguity is pointed out. Applications to recent data on the in-mediumwidth of omega mesons scattered on a Niobium target serve to determine unknown N*N-;(omega) in-medium coupling constants. The data are well described by N*(;)N(-1)self-energies contain-ing S-wave and P-wave N*(;) resonances. Exploratory investigations, however, show that the spectroscopic composition of self-energies depends crucially on the near-threshold properties of the width which at present is known only within large error bars. The calculations predict the prevalence of transversal self-energies, implying that vector currentcon servation is still maintained in the nuclear medium by slightly more than 90%. Schrodinger-equivalent potentials are derived and scattering lengths and effective range parameters are extracted for the longitudinal and transversal channel. Longitudinal and transversal spectral distributions are discussed and the dependencies on momentum and nucleardensity are investigated. Schrodinger-type omega+Nb-93 optical potentials are constructed. Low-energy parameters are deter-mined, are used to study the pole structure of the Smatrixat threshold. The effective range expansion of the omega-nucleus K-matrix led to a omega+Nb-93 bound states with bindingenergy Re(epsilon B)=-448 keV but of width Gamma(B)=4445 keV.