Pion Production in Neutrino-Nucleon Reactions.

We construct a model for the weak pion production off the nucleon, which in addition to the weak excitation of the Δ(1232) resonance and its subsequent decay into Nπ, it includes also some background terms required by chiral symmetry. We re-fit the C5A(q2) form factor to the flux averaged νμp→μ-pπ+ ANL q2-differential cross section data, finding a substantially smaller contribution of the Δ 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. [ABSTRACT FROM AUTHOR]