Sterile neutrinos

Abstract

Neutrino masses imply a likely existence of gauge-singlet fermions, which may be very heavy but may also be light. In the latter case, sterile neutrinos appear in the low-energy theory. They can make up all or part of dark matter and can explain the observed velocities of pulsars because they are emitted anisotropically from a cooling neutron star born in a supernova explosion. The most promising detection opportunity is by using x-ray telescopes and searching for monochromatic x-ray photons emitted from decays of these particles in dark-matter-dominated halos.