Angular distribution in neutrino-induced single pion production processes

A partial wave decomposition of \({v \mathord{\left/ {\vphantom {v {\bar v}}} \right. \kern-0em} {\bar v}}\) single pion production is used for studying resonant and nonresonant contributions. The dominant resonance excitation is dynamically described by a semirelativistic quark model. Nonresonant background is considered to arise from Born-terms diminuished by the lowest order partial waves (which are determined by resonances alone.) The method permits evaluation of interferences between resonance and background amplitudes as well as, more importantly, among resonances themselves. Predicted interference patterns are reflected by the pion angular distribution coefficients which compare well with recent data. Results obtained this way are also in agreement with momentum transfer measurements if higher resonance excitation form factors are chosen to resemble those tested in pion photoproduction, rendering simultaneously any nonresonant background small.