Next-generation neutrinoless double-beta (0 νββ ) decay experiments, with projected half-life sensitivities approaching 10 28 years, aim to probe the entire parameter space of the inverted neutrino mass ordering in the light-neutrino-exchange scenario. However, this reach remains uncertain by the substantial model dependence of the nuclear matrix elements (NMEs). In this work, we propose a strategy based on a combined analysis of 0 νββ decays to both the ground state and the first excited 0 + state of the daughter nucleus. We show that such a multi-channel approach can significantly enhance experimental sensitivity, depending on the underlying NME predictions. This method is particularly well suited for large liquid xenon detectors, such as the proposed PandaX-xT and XLZD experiments, which can efficiently identify transitions of 136 Xe to excited states. Our results highlight the importance of exploiting multiple decay channels in future 0 νββ searches to maximize their discovery potential.
Ding et al. (Mon,) studied this question.