Neutrino meets ultralight dark matter: 0??? decay and cosmology

We explore the neutrinoless double beta (0?? 00) decay induced by an ultralight dark matter field coupled to neutrinos. The effect on 0?? 00 decay is significant if the coupling violates the lepton number, for which the AL = 2 transition is directly driven by the dark matter field without further suppression of small neutrino masses. As the ultralight dark matter can be well described by a classical field, the effect features a periodic modulation pattern in decay events. However, we find that in the early Universe such coupling will be very likely to alter the standard cosmological results. In particular, the requirement of neutrino free-streaming before the matter-radiation equality severely constrains the parameter space, such that the future 0?? 00 decay experiments can hardly see any signal even with a meV sensitivity to the effective neutrino mass.

Automated summary

This study explores the neutrinoless double beta decay induced by an ultralight dark matter field coupled to neutrinos. The coupling violates lepton number and directly drives the AL=2 transition without suppressing small neutrino masses. However, this coupling is likely to alter the standard cosmological results in the early Universe, and the parameter space is severely constrained, making it difficult for future experiments to detect any signal even with a meV sensitivity to the effective neutrino mass.