Interactions of keV sterile neutrinos with matter

TL;DR

This paper explores how keV-scale sterile neutrinos, potential dark matter candidates, interact with matter and assesses the feasibility of detecting them directly through their weak interactions.

Contribution

It provides a detailed analysis of sterile neutrino interactions with matter via electroweak currents and evaluates the challenges in designing direct detection experiments.

Findings

Sterile neutrinos can ionize atoms and flip nuclear spins through weak interactions.

Detection rates are extremely low, making experimental observation very challenging.

The recoil momentum from sterile neutrino interactions depends on their mass.

Abstract

A sterile neutrino with mass of several keV is a well-motivated dark-matter candidate, and it can also explain the observed velocities of pulsars via anisotropic emission of sterile neutrinos from a cooling neutron star. We discuss the interactions of such relic particles with matter and comment on the prospects of future direct detection experiments. A relic sterile neutrino can interact, via sterile-active mixing, with matter fermions by means of electroweak currents, with the final state containing a relativistic active neutrino. The recoil momentum impacted onto a matter fermion is determined by the sterile neutrino mass and is enough to ionize atoms and flip the spins of nuclei. While this suggests a possibility of direct experimental detection, we calculate the rates and show that building a realistic detector of the required size would be a daunting challenge.