Probing the double-beta decay of \(^{104}\)Ru through precise Q-value measurements and nuclear matrix element calculations

Abstract

The Q value of the double-beta (\(\beta ^-\beta ^-\)) decay of \(^{104}\)Ru (\(Q_{\beta ^-\beta ^-}\)-value) was determined using the JYFLTRAP double Penning trap mass spectrometer employing the Phase-Imaging Ion Cyclotron Resonance (PI-ICR) method. The obtained value of 1297.705(36) keV is in agreement with the current literature value of 1299.4(27) keV but is over 70 times more precise. As a consistency check on a 100 eV level, we also measured the precisely known \(^{102}\)Pd double-electron capture Q value, \(Q_\textrm{ECEC}=1203.531(92)\) keV, which agrees with the literature value of 1203.47(4) keV. The measured Q value of \(^{104}\)Ru \(\beta ^-\beta ^-\) decay was used in calculations of the phase-space factors of the double-beta decay. Also, the nuclear matrix elements were calculated using the microscopic interacting boson model (IBM-2) as a nuclear model and compared with other available results. With these theoretical calculations based on the measured Q value, the estimates for the two-neutrino and neutrinoless double-beta decay half-lives of \(^{104}\)Ru were calculated to be \(t_{1/2}^{2\nu \beta \beta }>5.449\times 10^{21}\) years and \(t_{1/2}^{0\nu \beta \beta }>5.775\times 10^{26}\) years, respectively. The calculated \(2\nu \beta ^-\beta ^-\) half-life is longer than the current experimental lower limit but short enough to be potentially within reach with future high precision experiments.