Global Ab initio Neutrino Mass Limits from Neutrinoless Double-Beta Decay

We present global limits for Majorana neutrino masses by combining latest results from neutrinoless double-beta ($0\nu \beta \beta$) decay searches and ab initio nuclear theory. Limits are derived in a Bayesian framework utilizing likelihood functions from a suite of $0\nu \beta \beta$-decay experiments in conjunction with nuclear matrix elements calculated from nuclear and electroweak forces derived from chiral effective field theory and implemented in the in-medium similarity renormalization group many-body approach. In contrast to nuclear models, ab initio results indicate that the current generation of $0\nu \beta \beta$-decay experiments have likely $\mathit{\text{not}}$ yet reached sensitivities required to probe the mass regime allowed by neutrino-oscillation data, where the combined bounds are notably stronger than those given by individual experiments. Finally, from predicted sensitivities of next-generation searches, we show that, while no one individual experiment fully covers the inverted mass ordering, this can be achieved from combined contributions from the four key isotopes: ${}^{76}$Ge, ${}^{100}$Mo, ${}^{130}$Te, and ${}^{136}$Xe.