Direct detection of relic active and sterile neutrinos

TL;DR

This paper explores the potential for laboratory detection of relic active and sterile neutrinos using beta and EC decaying nuclei, analyzing capture rates and future experimental prospects like PTOLEMY.

Contribution

It provides detailed calculations of relic neutrino capture rates on specific nuclei within a flavor mixing framework, highlighting the feasibility of direct detection.

Findings

Relic neutrino capture rates are calculated for beta and EC decays.

Future experiments like PTOLEMY could potentially detect relic neutrinos.

Direct detection of hot dark matter via neutrino capture remains a long-term possibility.

Abstract

Both active and sterile sub-eV neutrinos can form the cosmic neutrino background in the early Universe. We consider the beta-decaying (e.g., $^3$H) and EC-decaying (e.g., $^{163}$Ho) nuclei as the promising targets to capture relic neutrinos in the laboratory. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta decay or electron capture (EC) decay backgrounds in the (3+$N_{\rm s}$) flavor mixing scheme, and discuss the future prospect in terms of the PTOLEMY project. We stress that such direct measurements of hot DM might not be hopeless in the long term.