On the correlation coefficient T(E_e) of the neutron beta decay, caused by the correlation structure invariant under discrete P, C and T symmetries
arXiv:2101.01014 · doi:10.1016/j.physletb.2021.136263
Abstract
We analyze the correlation coefficient T(E_e), which was introduced by Ebel and Feldman (Nucl. Phys. 4, 213 (1957)). The correlation coefficient T(E_e) is induced by the correlations of the neutron spin with the antineutrino 3-momentum and the electron spin with the electron 3-momentum. Such a correlation structure is invariant under discrete P, C and T symmetries. The correlation coefficient T(E_e), calculated to leading order in the large nucleon mass m_N expansion, is equal to T(E_e) = - 2 g_A(1 + g_A)/(1 + 3 g^2_A) = - B_0, i.e. of order |T(E_e)| ~ 1, where is the axial coupling constant. Within the Standard Model (SM) we describe the correlation coefficient at the level of 10^{-3} by taking into the radiative corrections of order O(α/π) or the outer model-independent radiative corrections, where αis the fine-structure constant, and the corrections of order O(E_e/m_N), caused by weak magnetism and proton recoil. We calculate also the contributions of interactions beyond the SM, including the contributions of the second class currents.
15 pages, some typos are corrected