Role of heavy-meson exchange in pion production near threshold

Abstract

Recent calculations of $s$-wave pion production have severely underestimated the accurately known $pp\to pp{\pi }^0$\ total cross section near threshold. In these calculations, only the single-nucleon axial-charge operator is considered. We have calculated, in addition to the one-body term, the two-body contributions to this reaction that arise from the exchange of mesons. We find that the inclusion of the scalar $\sigma$-meson exchange current (and lesser contributions from other mesons) increases the cross section by about a factor of five, and leads to excellent agreement with the data. The results are neither very sensitive to changes in the distorting potential that generates the $NN$ wave function, nor to different choices for the meson-nucleon form factors. We argue that $pp\to pp{\pi }^0$\ data provide direct experimental evidence for meson-exchange contributions to the axial current.

28 Pages, IU-NTC #93-07

References in corpus (1)

• On the pion-nucleon coupling constant

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