Neutrino induced weak pion production off the nucleon

TL;DR

This paper investigates neutrino-induced single-pion production off nucleons near the Delta resonance, incorporating chiral symmetry background terms and refining the axial form factor to better match experimental data.

Contribution

It introduces background terms consistent with chiral symmetry into the model and provides a new fit for the axial form factor, reducing its value by about 30%.

Findings

Background terms significantly affect all channels.

New axial form factor value aligns with quark models and lattice results.

Improved fit to ANL cross section data.

Abstract

We study neutrino induced one-pion production off the nucleon in and around the Delta resonance region. Apart from the Delta-pole mechanism we include background terms required by chiral symmetry. These background terms give sizeable 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 $C_5^A(0)=0.867\pm 0.075$ is some 30% smaller than the commonly accepted value. This correction is compatible with most quark model estimates and a recent lattice calculation