Pion absorption on the deuteron

Abstract

The total and differential cross sections for the absorption of positive pions on deuterons have been calculated for pion kinetic energies between 3 and 220 MeV. The model is based on perturbation theory and includes the backward-moving pion. We varied several parts of the dynamical input, like the πN T-matrix and the absorption formfactor, and studied the effect of relativistic definitions of the relative momentum and of the choice of subsystem energies. Because of positive interference, the contribution of the backward-moving pion doubles the cross sections. The definition of the relativistic relative momentum according to Aaron, Amado and Young is to be preferred over that of Wightman and Gårding. Also the off-shell behaviour of the πN interactions and the choice of subsystem energies influence the cross sections significantly. We need rather low values for the cutoff at the absorption vertex (0.4–0.5 GeV/ c) in order to fit the experimental data.