Mesonic Contribution to the Compton Scattering Amplitude for Heavy Nuclei

The contribution of mesonic exchange currents to nuclear Compton scattering is investigated within the framework of a Fermi gas model of nuclear matter in the non-relativistic limit. The additional interaction between the nucleons is accounted for by including two- and three-body diagrams. As a test of this model, the enhancement constant $\kappa$ is calculated. The full correlators for the central and tensor part of the nucleon-nucleon interaction due to pion exchange are obtained and the energy dependence of the amplitude is investigated. The contribution of the $\Delta$-excitation to the mesonic part of the Compton amplitude is calculated explicitely using an effective Hamiltonian in the static limit.Comment: 21 pages, Latex, 12 figures available at http://www.physik2.gwdg.de/lokales/Forschungsberichte/Theorie/Meso