Pion and nucleon propagators in finite nuclei with applications in pion scattering, pion production, and pion-nucleon interactions
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1986
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Abstract
We present a theory for interacting pions and nucleons based on relativistic quantum field theory and expressed as coupled integral equations among the single-particle propagators and the vertex. We show that, in the "local" approximation (which is very convenient but unfortunately violates crossing symmetry), these equations are only slightly more complicated than the Boltzmann equation, and therefore should be computationally feasible. In the more restrictive Migdal approximation we evaluate the pion propagator explicitly using a mean field model for the nucleons and show applications to low energy pion scattering from nuclei and "subthreshold" pion production. It is found, in agreement with pion optical potential results, that 40 Mev pions scatter primarily from the nuclear surface and are extremely sensitive to the density distribution in this region. We present a solution to the general problem of relativistic particle production from a spatially, temporally, and energetically finite source and en route, obtain a theorem concerning the angular distribution of the emitted particles; quantitative calculations for pion production are not yet completed. The applications we consider involve only pions, nucleons, and Δ's and are basically time independent models, however the generalization to include the higher mass mesons is straight-forward and the general equations are completely time-dependent. This theory, therefore, should contain a complete description of transport theory including fluctuations as well as mean properties.
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Major physics