$pp\to ppω$ reaction near threshold

Abstract

We analyze the total cross section data for $pp \to ppω$ near threshold measured recently at SATURNE. Using an effective range approximation for the on-shell $pp$ S-wave final state interaction we extract from these data the modulus $|Ω| = 0.53$ fm$^4$ of the threshold transition amplitude $Ω$. We present a calculation of various (tree-level) meson exchange diagrams contributing to $Ω$. It is essential that $ω$-emission from the anomalous $ωρπ$-vertex interferes destructively with $ω$-emission from the proton lines. The contribution of scalar $σ$-meson exchange to $Ω$ turns out to be negligibly small. Without introducing off-shell meson-nucleon form factors the experimental value $|Ω|=0.53$ fm$^4$ can be reproduced with an $ωN$-coupling constant of $g_{ωN}=10.7$. The results of the present approach agree qualitatively with the Jülich model. We also perform a combined analysis of the reactions $pp\to ppπ^0, pnπ^+, ppη, ppω$ and $pn\to pnη$ near threshold.

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