In Chapters 10–13, we have discussed (anti)neutrino interactions on the free nucleon target leading to quasielastic (Chapter 10), inelastic (Chapters 11 and 12), and deep inelastic scattering (Chapters 13) depending upon the energy transferred to the target and the four-momentum transfer squared. The study of such processes is important to understand the various basic weak interaction processes induced by (anti)neutrinos from the free nucleons and determine the quasielastic form factors, transition form factors, and the structure functions of the nucleon at the W N N(ZN N) vertex. In recent times, the study of (anti)neutrino reactions from the nuclear targets has been emphasized as almost all the present generation (anti)neutrino experiments use moderate to heavy nuclear targets like 12C, 16O, 40Ar, 56Fe, 208Pb, where the interactions take place with the nucleons that are bound inside the nucleus. Various experiments like MINERvA, NOvA, T2K, etc., are being performed in the few GeV energy region where the contribution to the scattering cross section comes from all the possible channels, viz., quasielastic, inelastic, and deep inelastic scattering processes. A good understanding of the nuclear cross sections would be very helpful in analyzing these experiments. The precision with which the basic neutrino–nucleon cross sections in nuclear targets are known is still not better than 20–30%.
Neutrino oscillation experiments measure events that are a convolution of
(i) energy-dependent neutrino flux and
(ii) energy-dependent cross section.
Moreover, the nuclear medium effects modulating the cross sections are energy dependent. Therefore, it is highly desirable that we understand the energy dependence of nuclear medium effects in neutrino scattering processes; this understanding will help in achieving the future goals of physicists involved in studying CP violation and the mass hierarchy problem in the phenomenology of neutrino oscillations (Chapter 18).
Broadly, we may divide nuclear processes induced by neutrinos into two categories. The first one is the exclusive reactions
where Zi (Z f ) is the charge of initial (final) nucleus. In this case, the final nucleus is left either in the ground state or in an excited state, which decays into some final nuclear states through electromagnetic or weak interactions by emitting photons or charged leptons which are observed.