Electroweak single-pion production off the nucleon: from threshold to high invariant masses

摘要

[Background] Neutrino-induced single-pion production (SPP) provides animportant contribution to neutrino-nucleus interactions, ranging fromintermediate to high energies. There exists a good number of low-energy modelsin the literature to describe the neutrinoproduction of pions in the regionaround the Delta resonance. Those models consider only lowest-order interactionterms and, therefore, fail in the high-energy region (pion-nucleon invariantmasses, $W$>2 GeV). [Purpose] Our goal is to develop a model for electroweak SPP off the nucleon,which is applicable to the entire energy range of interest for present andfuture neutrino-oscillation experiments. [Method] We start with the low-energy model of [Phys.Rev.D76,033005(2007)],which includes resonant contributions and background terms derived from thepion-nucleon Lagrangian of chiral-perturbation theory. Then, from thebackground contributions, we build a high-energy model using a Regge approach.The low- and high-energy models are combined, in a phenomenological way, into ahybrid model. [Results] The Hybrid model is identical to the low-energy model in the low-Wregion, but, for W>2 GeV, it implements the desired high-energy behaviordictated by Regge theory. We have tested the high-energy model by comparingwith one-pion production data from electron and neutrino reactions. The Hybridmodel is compared with electron-proton scattering data, with neutrino SPP dataand with the predictions of the NuWro Monte Carlo event generator. [Conclusions] Our model is able to provide satisfactory predictions of theelectroweak one-pion production cross section from pion threshold to high $W$.Further investigation and more data are needed to better understand themechanisms playing a role in the electroweak SPP process in the high-W region,in particular, those involving the axial current contributions.