The inelastic scattering processes of (anti)neutrinos from nucleons are relevant in the region starting from the neutrino energy corresponding to the threshold production of a single pion. For neutral current (NC) induced 1π production, this starts at Eth v(⊽) = 144.7 MeV for vl reactions. In the case of charged current (CC) induced 1π production, the threshold energy is higher because of the massive leptons produced in the final state; it corresponds 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 the production of strange mesons (K) and hyperons (Ⲩ) start; both of which are the most relevant inelastic processes in the region of a few GeV. These inelastic processes have been studied very extensively, both theoretically and experimentally, in various reactions induced by photons and electrons which probe the interaction of the electromagnetic vector currents with hadrons in the presence of other strongly interacting particles like mesons and hyperons. In weak processes induced by neutrinos and antineutrinos, the inelastic processes provide a unique opportunity to study the interaction of the weak vector as well as the axial vector currents with hadrons in the presence of strongly interacting particles like mesons and hyperons. Moreover, a study of these weak processes from nucleons and nuclei is of immense topical importance in the context of the present neutrino oscillation experiments being done with the accelerator and atmospheric neutrinos in the energy region of a few GeV. The specific reactions to be studied in the inelastic channels are the various processes induced by the charged and neutral weak currents 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 shown in Figures 11.1(a) and 11.1(b), where vl(⊽l) and l-(l+)
are leptons interacting through the W±(Z) exchanges with the nucleon (N) producing the final nucleon (N') and hyperons (Ⲩ) and mesons like pions (π) and kaons (K).