Double-Charge-Exchange Scattering of Pions from Nuclei

Abstract

Pions offer a unique possibility as probes of nuclear structure since they can exchange two units of electrical charge unaccompanied by other quantum numbers. We have calculated the double-charge-exchange cross section for the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}+{\mathrm{He}}^{3}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+3n$ in the impulse approximation using the Chew-Low model for the pion-nucleon interaction. Only the dominant 3-3 channel is retained. For incident pions in the energy region of several hundred MeV, values of the differential cross section of $\frac{{d}^{2}\ensuremath{\sigma}}{d\ensuremath{\Omega}\mathrm{dE}}\ensuremath{\approx}1\ensuremath{-}10$ \ensuremath{\mu}b/MeV are obtained for forward angles. Triple-scattering terms are also calculated and found to introduce corrections of 10% in $\frac{{d}^{2}\ensuremath{\sigma}}{d\ensuremath{\Omega}\mathrm{dE}}$. Similar results are obtained when the work is extended to the reaction ${\ensuremath{\pi}}^{+}+{\mathrm{O}}^{18}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}+{\mathrm{Ne}}^{18}$ using shell-model wave functions.