Direct Detection of the Cosmic Neutrino Background Including Light Sterile Neutrinos

TL;DR

This paper explores the potential for direct laboratory detection of the cosmic neutrino background, including light sterile neutrinos, through their distinct signatures in electron energy spectra during neutrino capture on tritium.

Contribution

It proposes a novel method to detect sterile neutrinos in the cosmic neutrino background via their effects on electron spectra in beta decay experiments.

Findings

Sterile neutrinos can produce detectable imprints in electron energy spectra.

The proposed detection method could distinguish active from sterile neutrinos.

Laboratory detection of the C$ u$B including sterile components is potentially feasible.

Abstract

Current cosmological data drop an interesting hint about the existence of sub-eV sterile neutrinos, which should be a part of the cosmic neutrino background (C$\nu$B). We point out that such light sterile neutrinos may leave a distinct imprint on the electron energy spectrum in the capture of relic electron neutrinos by means of radioactive beta-decaying nuclei. We examine possible signals of sterile neutrinos relative to active neutrinos, characterized by their masses and sensitive to their number densities, in the reaction $\nu^{}_e + ~^3{\rm H} \to ~^3{\rm He} + e^-$ against the corresponding tritium beta decay. We stress that this kind of direct laboratory detection of the C$\nu$B and its sterile component might not be hopeless in the long term.