Short range exchange contributions to the cross section forpp→ppπ0near threshold

The nuclear S-wave pion production is described by the axial charge density operator of the two-nucleon systen. It is shown that the short range axial exchange charge operator implied by the nucleon-nucleon interaction enhances the predicted cross section for the reaction pp→pp${\mathrm{\pi }}^0$ near threshold by factors 3–5. This suffices to explain most of the underprediction obtained with the single-nucleon and S-wave pion rescattering operator. The result implies that the cross section for pp→pp${\mathrm{\pi }}^0$ can provide direct information on the short range components of the nucleon-nucleon interaction.