Nuclear charge-exchange corrections to leptonic pion production in the (3, 3)-resonance region

We discuss nuclear charge-exchange corrections to leptonic pion production in the region of the (3, 3) resonance, both from a phenomenological viewpoint and from the evaluation of a detailed model for pion multiple scattering in the target nucleus. Using our analysis, we estimate the nuclear corrections needed to extract the ratio $R={[{σ}({{ν}}_{{μ}}+n{→}{{ν}}_{{μ}}+n+{{π}}⁰)+{σ}({{ν}}_{{μ}}+p{→}{{ν}}_{{μ}}+p+{{π}}⁰)]}{2{σ}({{ν}}_{{μ}}+n{→}{{μ}}^{{-}}+p+{{π}}⁰)}$ from neutral-current search experiments using $₁₃Al²⁷$ and other nuclei as targets.