Chiral perturbation approach to the pp-->pp pi 0 reaction near threshold.

Abstract

The usual theoretical treatments of the near-threshold {ital pp}{r_arrow}{ital pp}{pi}{sup 0} reaction are based on various phenomenological Lagrangians. In this work we examine the relationship between these approaches and a systematic chiral perturbation method. Our chiral perturbation calculation indicates that the pion rescattering term should be significantly enhanced as compared with the traditional phenomenological treatment, and that this term should have substantial energy and momentum dependence. An important consequence of this energy-momentum dependence is that, for a representative threshold kinematics and within the framework of our semiquantitative calculation, the rescattering term interferes destructively with the Born term in sharp contrast to the constructive interference obtained in the conventional treatment. This destructive interference makes theoretical cross sections for {ital pp}{r_arrow}{ital pp}{pi}{sup 0} much smaller than the experimental values, a feature that suggests the importance of the heavy-meson exchange contributions to explain the experimental data. {copyright} {ital 1996 The American Physical Society.}