Isobar-doorway model for pion-nucleus scattering

The isobar-doorway model, a phenomenological version of the isobar-doorway theory, is studied for pion-nucleus scattering. The model includes phenomenologically all the many-body effects in pion-nucleon resonance channel by introducing (3,3) isobar as an explicit nuclear constituent and treating 1Δ-(A-1)-nucleon states as the doorway-states. The terms not included in the model because of the doorway hypothesis are identified. These correspond to the pion true-absorption on two nucleons. These terms are estimated and found to be small. The parameters of the model for two different parameterizations are obtained by comparing the calculated and experimental elastic scattering differential cross sections. The physical significance of these parameters viz-a-viz pion-nuclear dynamics is discussed