Introduction

The inelastic scattering processes of (anti)neutrinos from nucleons arerelevant in the region starting from the neutrino energy corresponding tothe threshold production of a single pion. For neutral current (NC) induced1π production, this starts at Ethv(⊽) = 144.7 MeV forvl reactions. In the case of charged current(CC) induced 1π production, the threshold energy ishigher because of the massive leptons produced in the final state; itcorresponds to Ev (⊽)≥ 150.5 MeV (277.4 MeV) for ve(nm) reactions. As the neutrino energy increases,inelastic processes of multiple pion production, viz.,2π, 3π, etc., and theproduction of strange mesons (K) and hyperons(Ⲩ) start; both of which are the most relevantinelastic processes in the region of a few GeV. These inelastic processeshave been studied very extensively, both theoretically and experimentally,in various reactions induced by photons and electrons which probe theinteraction of the electromagnetic vector currents with hadrons in thepresence of other strongly interacting particles like mesons and hyperons.In weak processes induced by neutrinos and antineutrinos, the inelasticprocesses provide a unique opportunity to study the interaction of the weakvector as well as the axial vector currents with hadrons in the presence ofstrongly interacting particles like mesons and hyperons. Moreover, a studyof these weak processes from nucleons and nuclei is of immense topicalimportance in the context of the present neutrino oscillation experimentsbeing done with the accelerator and atmospheric neutrinos in the energyregion of a few GeV. The specific reactions to be studied in the inelasticchannels are the various processes induced by the charged and neutral weakcurrents of neutrinos and antineutrinos, given in Table 11.1.

The first four reactions in Table 11.1 are strangeness conserving (∆S= 0) reactions and the last one is a strangeness changing (∆S = 1)reaction. The generic Feynman diagrams describing these reactions are shownin Figures 11.1(a) and 11.1(b), wherevl(⊽l) andl-(l+)

are leptons interacting through theW±(Z) exchanges withthe nucleon (N) producing the final nucleon(N') and hyperons(Ⲩ) and mesons like pions(π) and kaons (K).