a Pole Dominance Model of Pion Photoproduction in Nuclei.
Abstract
In the following work we investigate the possibility of explaining pion photoproduction using a simple pole model. The pole propagators we consider are those that exist near the production threshold energy, namely the single pion, nucleon, and delta propagators. We leave the mass, width, and coupling constant of the delta as free parameters. When these are fit we achieve fair agreement with the data. Our fitted values are close to other calculations of these quantities which exist in the literature. We next discuss the position of our model in a more complete calculation which includes the energy dependence of the mass and width of the 3-3 resonance. We explain why our choice of pseudovector coupling prevents extending our model except in a highly phenomenological manner. We discuss, formalistically, the application of our model to nuclei. The nuclear amplitude in momentum space is developed, and a method is found for folding in, using a perturbative approach, the effect of neighboring nuclei on the pole propagators. We conclude with a brief discussion of the Cloudy Bag Model as a calculational tool which removes many of the divergences that plague our model, and which we believe will provide the next major advance in photoproduction theory.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 1986
- Bibcode:
- 1986PhDT........43C
- Keywords:
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- Physics: Nuclear