Neutrino meets ultralight dark matter: $\boldsymbol{0\nu\beta\beta}$ decay and cosmology

TL;DR

This paper investigates how ultralight dark matter coupling to neutrinos could induce neutrinoless double beta decay with a distinctive periodic pattern, but cosmological constraints limit the detectability of such signals in future experiments.

Contribution

It introduces a novel mechanism where ultralight dark matter causes lepton number violating neutrinoless double beta decay with observable periodic modulation, constrained by cosmological considerations.

Findings

Dark matter coupling induces periodic modulation in decay events.

Cosmological constraints limit the parameter space for detectable signals.

Future experiments are unlikely to observe signals due to early Universe constraints.

Abstract

We explore the neutrinoless double beta ($0\nu \beta\beta$) decay induced by an ultralight dark matter field coupled to neutrinos. The effect on $0\nu\beta\beta$ decay is significant if the coupling violates the lepton number, for which the $\Delta L=2$ 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 $0\nu \beta\beta$ decay experiments can hardly see any signal even with a meV sensitivity to the effective neutrino mass.