Sterile Neutrino/Dark Fermion Dark Matter: Searches in the X-Ray Sky, the Nuclear Physics Laboratory and in Galaxy Formation

Abstract

The possibility of dark matter being a particle involved in the generation of neutrino mass has been of interest for over 25 years. Sterile neutrinos—or in the contemporary parlance—dark fermions, are among the simplest and most cited particles which can provide a mechanism for neutrino mass. If one particle of this class has a small mixing, it can be quasi-thermally or nonthermally produced in the early Universe, affect cosmological structure formation, and be detected by X-ray telescopes or laboratory nuclear experiments. A candidate line was detected in 2014, and I review the status of the line and its implications for galaxy formation, proposals for future observations, and laboratory detection.