Abstract
The ^{98}Mo double-beta decay Q-value has been measured, and the corresponding nuclear matrix elements of neutrinoless double-beta (0nu beta beta ) decay and the standard two-neutrino double-beta (2nu beta beta ) decay have been provided by nuclear theory. The double-beta decay Q-value has been determined as Q_{beta beta }=113.668(68) keV using the JYFLTRAP Penning trap mass spectrometer. It is in agreement with the literature value, Q_{beta beta }=109(6) keV, but almost 90 times more precise. Based on the measured Q-value, precise phase-space factors for 2nu beta beta decay and 0nu beta beta decay, needed in the half-life predictions, have been calculated. Furthermore, the involved nuclear matrix elements have been computed in the proton–neutron quasiparticle random-phase approximation (pnQRPA) and the microscopic interacting boson model (IBM-2) frameworks. Finally, predictions for the 2nu beta beta decay are given, suggesting a much longer half-life than for the currently observed cases.
Highlights
Particle physics by two units, since two leptons are created
The neutrinoless mode is under intense searches by several large-scale experiments worldwide [10–16], with the most stringent half-life limits given by t10/ν2 1026 years, while the measured half-lives of 2νββ decay are in the order of t12/ν2 ∼ 1018 − 1024 years [1]
Life expressions of these decay modes, were calculated in the proton-neutron quasiparticle random-phase approximation (pnQRPA) and IBM-2 frameworks. Within both frameworks we take the isospin restoration into account by forcing the Fermi matrix element of the 2νββ decay to vanish
Summary
The neutrinoless mode is under intense searches by several large-scale experiments worldwide [10–16], with the most stringent half-life limits given by t10/ν2 1026 years, while the measured half-lives of 2νββ decay are in the order of t12/ν2 ∼ 1018 − 1024 years [1] Another intriguing aspect of 0νββ decay is that the half-life of the process is inversely proportional to the square of the effective Majorana mass, which depends on the neutrino masses. We calculate the NMEs for the two decay modes in two different theory frameworks that are well established for calculating the NMEs in medium-heavy to heavy nuclei: proton-neutron quasiparticle random-phase approximation (pnQRPA) [25,26] and microscopic interacting boson model (IBM-2) [27,28] This is the first time the 98Mo double-beta decay matrix elements are calculated in no-core pnQRPA and IBM-2 frameworks. Due to the low Q-value, the 2νββ-decay has not been measured – we give estimates for both the 2νββ-decay and 0νββdecay half-lives based on the calculated NMEs and phasespace factors
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