A review of phenomenological models for pion production on nuclei with protons incident at intermediate energies
Date
1977
Authors
Lim, Diana Joyce
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Abstract
Phenomenological models for single pion production from proton collisions with nuclei at rest are reviewed. The incident energies considered are from threshold to approximately 800 MeV. Due to the short range of the strong interaction at these energies, compared with internucleon distances in the nuclei, the scattering with a nucleus is highly incoherent, and the production is predominantly the single nucleon-nucleon interaction (ie. the impulse approximation). Modifications of the free nucleon-nucleon interaction due to the nuclear medium, such as the inclusion of the Fermi motion of the target nucleon, multiple scattering effects and nuclear potentials, are included in an ad hoc manner. The upper energy limit of 800 MeV for the models considered, restricts the dominant production mechanism to the formation of the Δ(1236) isobar in the intermediate state.
Due to the limited available data, the models considered are concerned only with the characteristics of the emerging pion, and the final state of the nucleus is ignored. This often results in one or more free parameters which may give reasonably good fits to experimental data, but this correlation may have little physical meaning. Certain aspects of the production mechanisms and of nuclear structure can, however, be investigated successfully with these models. More success can be expected with models in which the final state of the nucleus is taken into account.