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Nucleon Resonance Effects in $pp\to ppπ^0$ near Threshold

M. T. Peña·D. O. Riska·A. Stadler
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Abstract

The role of the low lying nucleon resonances beyond the $Δ(1232)$ in the reaction $pp\to ppπ^0$ near threshold is shown to be numerically significant by a calculation, which takes into account the pion re-scattering contribution described by chiral perturbation theory and the short-range mechanisms that are implied by the nucleon-nucleon interaction model. The intermediate N(1440) (P$_{11}$) resonance is excited by the short-range exchange mechanisms, while the N(1535) ($S_{11}$) and N(1520) ($D_{13}$) resonances are excited by $η$ and $ρ$ meson exchange, respectively. The $P_{11}$ increases the calculated cross section, whereas the $S_{11}$ and $D_{13}$ resonances decrease it. The calculation takes full account of the initial and final state interactions.

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M. T. Peña, D. O. Riska, A. Stadler. 1999-07-26. Nucleon Resonance Effects in $pp\to ppπ^0$ near Threshold. https://doi.org/10.1103/physrevc.60.045201

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