Confronting the low-scale seesaw and leptogenesis with neutrinoless double beta decay

TL;DR

This paper examines how heavy neutrinos influence neutrinoless double beta decay and how upcoming experiments can constrain neutrino properties, impacting theories of leptogenesis and the neutrino mass hierarchy.

Contribution

It provides a detailed analysis of the constraints on heavy neutrino parameters from neutrinoless double beta decay, considering both normal and inverted neutrino mass hierarchies.

Findings

Next-generation $0 uetaeta$ experiments can significantly restrict heavy neutrino parameter space.

Leptogenesis requirements further narrow the allowed regions in the parameter space.

Mass splitting of heavy neutrinos can be probed at current and future accelerator experiments.

Abstract

We revisit the impact of heavy neutrinos with masses in the MeV-GeV range on neutrinoless double beta decay ($0\nu\beta\beta$) in view of updated results for the lifetime of this process. Working in a minimal realistic extension of the Standard Model by two right-handed neutrino flavours, we show that the non-observation of $0\nu\beta\beta$ will impose strong bounds on the heavy neutrino properties that are complementary to the limits obtained from Big Bang Nucleosynthesis and collider searches. For an inverted mass hierarchy of the light neutrinos we find that improved limits on $0\nu\beta\beta$ from next-generation experiments, assuming an improvement of two orders of magnitude on the current $0\nu\beta\beta$ limits will restrict the allowed parameter space for fixed mass splitting to narrow bands in the mass-mixing plane. Further combining this with the requirement to explain the baryon asymmetry of the universe via leptogenesis reduces these bands to windows in parameter space that are constrained in all directions and can be targeted by direct searches at accelerators, and restricts the mass splitting to values that can be resolved at experiments. For a normal mass hierarchy, restricting the allowed parameter will require even stronger $0\nu\beta\beta$ limits, and only parts of the parameter space can then be probed.