NEUTRINO-INDUCED WEAK PION PRODUCTION OFF THE NUCLEON

We study neutrino-induced one-pion production off the nucleon in and around the Delta resonance region. A part from the Delta-pole mechanism we include background terms required by chiral symmetry. These background terms give size able contributions in all channels. To better reproduce the ANL q(2)-differential cross section data, we make a new fit of the C-5(A)(q(2)) axial nucleon to Delta form factor. The new result C-5(A)(0) = 0.867 +/- 0.075 is some 30% smaller than the commonly accepted value. This correction is compatible with most quark model estimates and a recent lattice calculation.(1)