An Analytic Distorted Wave Approximation for Electropion and Photopion Production on 12C near Threshold

Abstract

An analytic distorted wave approximation (ADWA) that can be used to analyse photopion and electropion production cross sections is developed. An application is made to analyse data from 12C near threshold once the approximation scheme is established as a realistic replacement for the more usual, distorted wavefunctions given by the optical model for low energy pion scattering. The pion production data analyses made using a generalized Helm model for the transition densities clearly demonstrates the significant role of distortion effects and that the ADW A is a good and simple representation of these effects. Repeating the analyses using microscopic models of nuclear structure indicates inadequacies in those structure specifications.