New Analysis of the Second-class Current in the Radiative Scattering Process of Neutrinos (and Antineutrinos) by Atomic Nuclei

Abstract

The study of the radiative neutrino(antineutrino)-nucleus scattering process on the lithium-6 nucleus (6Li) allowed us to derive the general expression of the differential cross section for this type of process and to highlight several significant results. In particular, the analysis focused on the influence of the tensor form factor FT , associated with the second-class currents (SCCs), on two key observables: the charge asymmetry coefficient and the degree of polarization of the emitted photon. The study of the charge asymmetry coefficient Aν˜ν reveals a strong dependence on the presence of the tensor form factor. In the absence of SCCs (FT = 0), the behavior of Aν˜ν remains moderate and stable as a function of the neutrino energy. Conversely, when FT \(\neq\) 0, the coefficient increases significantly and exhibits pronounced variations, including sign changes at high energy. The analysis of the relative contribution δAν˜ν confirms this trend, emphasizing an enhanced sensitivity to SCCs, particularly in the high-energy domain (Eν ≳ 200 MeV). The examination of the photon polarization degree PSγ also shows that it serves as a relevant indicator of the presence of SCCs. The introduction of a nonzero tensor form factor (FT = 5 × 10−3 MeV−1) leads to substantial modifications of the polarization degree. The analysis of the relative contribution δPSγ further confirms this strong sensitivity, with variations exceeding 200% at high energy.