Neutrinos as Hot or Warm Dark Matter

TL;DR

This paper explores the potential of using beta and electron capture decays to detect relic neutrinos, which could serve as hot or warm dark matter, and discusses the feasibility of laboratory measurements for these elusive particles.

Contribution

It proposes specific nuclear decay processes as promising targets for detecting relic neutrinos and calculates their capture rates across different flavor mixing schemes.

Findings

Capture rates depend on flavor mixing schemes.

Detection of relic neutrinos remains challenging but potentially feasible.

Laboratory measurements of hot or warm dark matter neutrinos are possible in the long term.

Abstract

Both active and sterile sub-eV neutrinos can serve for hot dark matter (DM). On the other hand, keV sterile neutrinos could be a good candidate for warm DM. The beta-decaying (e.g., H-3 and Ru-106) and EC-decaying (e.g., Ho-163) nuclei are considered as the most promising targets to capture those extremely low energy neutrinos and antineutrinos, respectively. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta-decay or EC-decay backgrounds in different flavor mixing schemes. We stress that such direct laboratory measurements of hot or warm DM might not be hopeless in the long term.