High-precision $Q$-value measurement and nuclear matrix elements for the double-$β$ decay of $^{98}$Mo

Neutrinoless double-beta ($0νββ$) decay and the standard two-neutrino double-beta ($2νββ$) decay of $^{98}$Mo have been studied. The double-beta decay $Q$-value has been determined as $Q_{ββ}=113.668(68)$ keV using the JYFLTRAP Penning trap mass spectrometer. It is in agreement with the literature value, $Q_{ββ}=109(6)$ keV, but almost 90 times more precise. Based on the measured $Q$-value, precise phase-space factors for $2νββ$ decay and $0νββ$ 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 $2νββ$ decay are given, suggesting a much longer half-life than for the currently observed cases.