Double-Charge-Exchange Scattering of Low-Energy Pions by Nuclei

The double-charge-exchange cross section for the scattering of low-energy pions by nuclei is calculated in second Born approximation, considering only $s$-wave scattering of the pions by individual nucleons. The differential cross section for pions of energy 20 to 40 MeV, and a light target with two neutrons outside a closed shell, is calculated to be ∼7 μb/sr, with considerable enhancement for targets with larger neutron excess. The scattering to the isobaric analog of the target ground state is strongly favored.