Two-Neutrino Double Beta Decay with Sterile Neutrinos

TL;DR

This paper explores how sterile neutrinos influence two-neutrino double beta decay, analyzing energy and angular distributions, and deriving constraints on sterile neutrino properties from current and future experiments.

Contribution

It investigates the effects of sterile neutrinos on double beta decay observables and provides updated limits on active-sterile mixing and right-handed couplings.

Findings

Sterile neutrinos alter energy distributions at the kinematic endpoint.

Current data constrains active-sterile mixing parameters.

Future experiments could improve sensitivity to sterile neutrino properties.

Abstract

Usually considered a background for experimental searches for the hypothetical neutrinoless double beta decay process, two-neutrino double beta decay nevertheless provides a complementary probe of physics beyond the Standard Model. In this paper we investigate how the presence of a sterile neutrino, coupled to the Standard Model either via a left-handed or right-handed current, affects the energy distribution and angular correlation of the outgoing electrons in two-neutrino double beta decay. We pay particular attention on the behaviour of the energy distribution at the kinematic endpoint and we estimate the current limits on the active-sterile mixing and effective right-handed coupling using current experimental data as a function of the sterile neutrino mass. We also investigate the sensitivities of future experiments. Our results complement the corresponding constraints on sterile neutrinos from single beta decay measurements in the 0.1 - 10 MeV mass range.