Nuclear Structure Effects on the Suppression of Two-Neutrino Double Beta Decay
Neutrinoless double beta decay is expected to clarify the fundamental nature of the neutrino. In deducing quantities such as the neutrino mass, the nuclear part of the transition amplitude has to be calculated theoretically. A test of nuclear struc ture calculations is provided by the two-neutrino double beta (2v ββ decay which is free from unknown physical quantities on the particle physics side. It is shown, by applying the proton-neutron quasiparticle RPA model, that the 2v ββ decay rate is strongly suppressed by particle-hole correlations in the ground states of parent and daughter nuclei. Mainly responsible for the ground-state correlations is the parti cle-particle interaction. We have adjusted its strength to experimental Gamow-Teller strengths of β+ decays of nuclei with mass number A = 60−160 and obtain with this strength calculated 2v ββ half-lives consistent with experiment. The long standing discrepancy between theoretical and experimental half-lives by a large fac tor up to two orders of magnitude seems to be resolved.
KeywordsNeutrino Mass Majorana Neutrino Neutrinoless Double Beta Decay Nuclear Matrix Element Quasiparticle Random Phase Approximation
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