What can we learn from recent 2ν β β experiments?*

Abstract

Abstract Recent measurements of the two neutrino double beta decay high precision electron spectra, combined with charge exchange or β-decay experimental data, have revealed severe constraints across current nuclear many body calculations. Our calculations show that the quasi-particle random phase approximation (QRPA) approach can adequately reproduce the measured spectra for the two open shell nuclei, Se and Mo. For the closed shell nucleus Xe, QRPA can also reproduce the spectra with proper treatments. Considering the high-lying state reduction, we also find that the nuclear shell model can also adequately reproduce the spectra and Gamow-Teller transition strength under a unique quenched axial-vector coupling constant . For Xe, we find that flipping the sign for the decay strength causes the spectra to go beyond the so-called high-lying state dominance hypothesis. These results call for future high precision measurements of charge-exchange reactions.