Possible Capture of keV Sterile Neutrino Dark Matter on Radioactive beta-decaying Nuclei

TL;DR

This paper explores the potential for detecting keV sterile neutrino dark matter through its capture on radioactive beta-decaying nuclei, proposing a feasible laboratory detection method by analyzing electron spectra.

Contribution

It introduces a self-consistent framework for active-sterile neutrino mixing and assesses the experimental prospects of detecting keV sterile neutrinos via capture reactions.

Findings

Distinct signatures in electron energy spectra from neutrino capture on radioactive nuclei.

Analysis suggests laboratory detection of keV sterile neutrinos is potentially feasible.

Provides a new approach to search for warm dark matter candidates in laboratory experiments.

Abstract

There exists an observed "desert" spanning six orders of magnitude between O(0.5) eV and O(0.5) MeV in the fermion mass spectrum. We argue that it might accommodate one or more keV sterile neutrinos as a natural candidate for warm dark matter. To illustrate this point of view, we simply assume that there is one keV sterile neutrino nu_4 and its flavor eigenstate nu_s weakly mixes with three active neutrinos. We clarify different active-sterile neutrino mixing factors for the radiative decay of nu_4 and beta decays in a self-consistent parametrization. A direct detection of this keV sterile neutrino dark matter in the laboratory is in principle possible since the nu_4 component of nu_e can leave a distinct imprint on the electron energy spectrum when it is captured on radioactive beta-decaying nuclei. We carry out an analysis of its signatures in the capture reactions nu_e + ^{3}H \to ^{3}He + e^- and nu_e + ^{106}Ru \to ^{106}Rh + e^- against the beta-decay backgrounds, and conclude that this experimental approach might not be hopeless in the long run.