Final state interactions and the charge dependence of (π, πN) reactions from nuclei

Abstract

The theory of pion quasi-elastic scattering leading to nucleon emission from nuclei at pion energies near the (3, 3) resonance energy is investigated. The importance of final state interactions between the outgoing nucleon and the residual nucleus is studied with particular emphasis on the relative cross sections for the reactions A( π +, πN) and A( π −, πN) and also for the reactions A( π −, π − n) and A( π −, π − p) which produce mirror nuclei in the final state. A reasonably consistent description of the available data is obtained only if compound nucleus effects are included in the final state interaction. Using an isospin basis the remarkable deviations from the simple plane wave impulse approximation theory observed in several experiments are seen to arise from the complete coherence assumptions inherent in the plane wave approach. Predictions from the present approach are made for target nuclei with nonzero neutron excess for both (π, πN) and (π, π′) processes.