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.
Highlights
Sterile neutrinos are among the most sought-after candidates of exotic particles
Considered a background for experimental searches for the hypothetical neutrinoless double beta decay process, two-neutrino double beta decay provides a complementary probe of physics beyond the Standard Model
Useful probes include the cosmic microwave background (CMB) shift parameter RCMB, the first peak of the baryon acoustic oscillations (BAO) and the Hubble parameter HðzÞ inferred from type Ia supernovae, BAO and Lyman-α data
Summary
Sterile neutrinos are among the most sought-after candidates of exotic particles. The main motivation for their existence is the fact that the Standard Model (SM) does not contain right-handed (RH) counterparts of the left-handed (LH) neutrino states participating in electroweak interactions, in contrast to the quarks and charged leptons. In this work we assess the potential of 0νββ decay experiments being sensitive to kinks in the background two-neutrino double beta (2νββ) decay spectrum caused by the presence of sterile neutrinos in the final state with masses mN ≲ 1 MeV. In addition to a truly sterile neutrino, i.e., one that inherits the SM charged-current Fermi interaction albeit suppressed by the active-sterile mixing, we consider RH current interactions of the “sterile” neutrino, e.g., arising in left-right symmetric models. Such interactions change the angular distribution of the electrons emitted in 2νββ decay [9].
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