The (π, 2π) reaction and spin-isospin strength distribution in nuclei

Abstract

Pion production on nuclei within the distorted-wave impulse approximation is studied, by using the local density approximation (LDA) for the treatment of possible nuclear spin-isospin mode enhancements, to which this process is known to be sensitive. The basic amplitude is based on a one-nucleon mechanism, since two-nucleon processes are here estimated to be relatively small. Various discrete pionlike levels (J P =0−, 1+, 2−, …;T=1) are studied and compared with nonpionlike ones, and the cross-sections for these discrete excitations are quite small. Inclusive cross-sections —also sensitive to possible spin-isospin enhancements—are considerably larger ((0.1÷10)mb). The quasi-free peak plays a dominant role in the inclusive cross-section, as demonstrated within the Fermi-gas model. All cases are studied as a function ofg′, the Migdal spin-isospin parameter.