Prospects for the direct detection of the cosmic neutrino background

TL;DR

This paper reviews the prospects for directly detecting the cosmic neutrino background using weak interaction techniques, highlighting current technological limitations and future experimental possibilities.

Contribution

It provides a comprehensive overview of existing detection methods and assesses their feasibility with current and future technology.

Findings

Current detection proposals are several orders of magnitude away from being feasible.

Neutrino capture on beta decaying nuclei is the most promising future approach.

Existing indirect evidence supports the cosmic neutrino background's existence.

Abstract

The existence of a cosmic neutrino background -- the analogue of the cosmic microwave background -- is a fundamental prediction of standard big bang cosmology. Up to now, the observational evidence for its existence is rather indirect and rests entirely on cosmological observations of, e.g., the light elemental abundances, the anisotropies in the cosmic microwave background, and the large scale distribution of matter. Here, we review more direct, weak interaction based detection techniques for the cosmic neutrino background in the present epoch and in our local neighbourhood. We show that, with current technology, all proposals are still off by some orders of magnitude in sensitivity to lead to a guaranteed detection of the relic neutrinos. The most promising laboratory search, based on neutrino capture on beta decaying nuclei, may be done in future experiments designed to measure the neutrino mass through decay kinematics.