π−Capture byHe3and the Two-Nucleon Capture Model

Abstract

The rates of capture of ${\ensuremath{\pi}}^{\ensuremath{-}}$ mesons by ${\mathrm{He}}^{3}$ leading to the final states $d+n$ and $p+n+n$ are calculated using a phenomenological two-nucleon Hamiltonian for the capture interaction $\ensuremath{\pi}\mathrm{NN}\ensuremath{\rightarrow}\mathrm{NN}$, obtained previously by Eckstein from an analysis of the experimental data on the inverse process of one-pion production in nucleon-nucleon collisions. Both $S$- and $P$-orbit captures are considered and it is shown that $P$-orbit capture does not compete with the $P\ensuremath{\rightarrow}S$ radiative transition. The radiative capture rate ${W}_{\ensuremath{\gamma}}$ (for final state ${\mathrm{H}}^{3}$+$\ensuremath{\gamma}$) is computed in terms of the photoproduction amplitude of Chew, Goldberger, Low, and Nambu and is used to deduce the nucleonic absorption rate ${W}_{\mathrm{abs}}={W}_{d}+{W}_{p}$ from the ratio $\frac{{W}_{\mathrm{abs}}}{{W}_{\ensuremath{\gamma}}}$ measured experimentally. The agreement between calculation and experiment for ${W}_{\mathrm{abs}}$ is satisfactory. Our conclusion is that the form of close pair correlations in nuclei is essentially the same as that for the "free" nucleon-nucleon interaction and is comparatively insensitive to the presence of other nucleons.