Pion Production in Neutrino-Nucleon Reactions

Abstract

We construct a model for the weak pion production off the nucleon, which in addition to the weak excitation of the $\hat{I}”(1232)$ resonance and its subsequent decay into $N\ddot{I}€$, it includes also some background terms required by chiral symmetry. We re-fit the $C_5^A(q^2)$ form factor to the flux averaged $\hat{I}{½}_{\hat{I}}¼p\to \hat{I}{¼}^{-}p\ddot{I}{€}^{+}$ ANL $q^2-$differential cross section data, finding a substantially smaller contribution of the $\hat{I}”$ pole mechanism than traditionally assumed in the literature. We also show that the interference between the Delta pole and the background terms produces parity-violating contributions to the pion angular differential cross section.

To appear in the proceedings of Fifth International Workshop on. Neutrino-Nucleus Interactions in the Few-GeV Region. May 30, 2007 - June 3, 2007. Fermilab, Batavia, Illinois USA