Sterile Neutrino Dark Matter

Abstract

We review sterile neutrinos as possible Dark Matter candidates. After a short summary on the role of neutrinos in cosmology and particle physics, we give a comprehensive overview of the current status of the research on sterile neutrino Dark Matter. First we discuss the motivation and limits obtained through astrophysical observations. Second, we review different mechanisms of how sterile neutrino Dark Matter could have been produced in the early universe. Finally, we outline a selection of future laboratory searches for keV-scale sterile neutrinos, highlighting their experimental challenges and discovery potential.

Axion-Sterile-Neutrino Dark Matter

“…4 (dashed lines). The X-ray bounds are the upper ones in blue [24] and red [60], while the phase-space ones are the lower ones in black.…”

“…Using known results of the literature (see Ref. [24] for a review) one obtains, within this approximation…”

“…The θ α1 are the elements of the matrix Θ ≡ m D M −1 . It is convenient to introduce a total mixing parameter θ defined by [24]…”

“…[59] for a related study). The most recent publications providing this type of X-ray bounds used the data collected by the NuSTAR satellite, a space-based X-ray telescope, observing the Milky Way (see [24] for a review) and, more recently, the Andromeda galaxy (M31) [60]. We will take these bounds into account in Sec.…”

“…The first two are the non-resonant [20] and resonant [21] production mechanisms, which occur thanks to the mixing between such sterile neutrino and the active neutrinos of the SM (see Refs. [22][23][24] for reviews). The third one takes place in a recently proposed CPT-symmetric universe [25,26], where inflation and the above-mentioned mixing are not required.…”