GT SD and high multipole nuclear matrix elements for double beta decays and astro neutrino nuclear interactions

Abstract

Nuclear matrix elements (NMEs) for GT (Gamow Teller), spin dipole (SD) and higher multipole transitions are associated with double beta decays and astro neutrino nuclear interactions. They are reduced with respect to quasi-particle (QP) NMEs by a factor k ≈ 0.2-0.3. The reduction coefficient k is discussed in terms of the nucleonic spin isospin correlations and the non-nucleonic nuclear medium effects. The latter may be incorporated by the effective (quenching) factor gAeff/gAfree. The SD NMEs derived from the (3He,t) charge exchange reactions (CERs) are consistent with the empirical NMEs M(S D) based on the quasi-particle model with the empirical effective SD coupling constant k. The SD NMEs derived from CERs are reduced uniformly in the wide momentum range of q ≈20-100 MeV/c. Impacts of the universal reduction(quenching) on NMEs for neutrino-less DBDs and low and medium energy astro neutrinos are discussed.