Pion-nucleus many-body problem

New aspects of pion-nucleus scattering are studied within the confines of a virtual rho exchange model, a dominant role being played by short-range correlations. A simplified treatment of double scattering terms is followed by a discussion of scattering through the Δ(1236) isobar. A more general view is provided by a multiple scattering expansion via iteration of the Klein-Gordon equation in powers of the Kisslinger optical potential. This leads to the conclusion that for K much less than m/sub π/, the impulse approximation should be valid. Through a many-body framework, range effects are studied for the πNA vertex and effects of antisymmetry are shown to allow exchange of other mesons. This approach is then related to the Migdol theory of finite Fermi systems. The effects of a laboratory center of mass transformation coupled with short-range correlations are seen to yield a new term in the first order optical potential. Finally, experimental π-nucleus cross sections are discussed along with the importance of various terms in the optical potential