Reaction pp-->n Delta ++: Observables and model predictions.

Abstract

A recent analysis of exclusive pion production in proton-proton scattering allows for the direct comparison of theory with pp\ensuremath{\rightarrow}n${\mathrm{\ensuremath{\Delta}}}^{++}$ observables. We have extracted NN\ensuremath{\rightarrow}N\ensuremath{\Delta} transition amplitudes from the Bonn meson-exchange model and calculated differential cross section and asymmetry for this reaction. In particular, we establish correlations between the asymmetry and the phases of the major inelastic transition amplitudes. We find evidence that the phases of the transition amplitude $^{3}$${\mathit{F}}_{3}$(NN)${\ensuremath{\rightarrow}}^{5}$${\mathit{P}}_{3}$(N\ensuremath{\Delta}) are responsible for the large discrepancy between theory and experiment in the asymmetry around 800 MeV incident laboratory kinetic energy. We also suggest how the theory can be improved.