Dark matter's X-files

TL;DR

This paper explores sterile neutrinos as a candidate for dark matter, discussing their production mechanisms, observational signatures via X-ray emissions, and implications for cosmic structure formation.

Contribution

It introduces the idea that keV-scale sterile neutrinos produced from Higgs decays can serve as cold dark matter and discusses their potential observational signatures.

Findings

Sterile neutrinos can be dark matter candidates with detectable X-ray lines.

Production from Higgs decays results in colder dark matter than neutrino oscillation mechanisms.

X-ray observations can constrain sterile neutrino properties and their role in early star formation.

Abstract

Sterile neutrinos with keV masses can constitute all or part of the cosmological dark matter. The electroweak-singlet fermions, which are usually introduced to explain the masses of active neutrinos, need not be heavier than the electroweak scale; if one of them has a keV-scale mass, it can be the dark-matter particle, and it can also explain the observed pulsar kicks. The relic sterile neutrinos could be produced by several different mechanisms. If they originate primarily from the Higgs decays at temperatures of the order of 100 GeV, the resulting dark matter is much ``colder'' than the warm dark matter produced in neutrino oscillations. The signature of this form of dark matter is the spectral line from the two-body decay, which can be detected by the X-ray telescopes. The same X-rays can have other observable manifestations, in particular, though their effects on the formation of the first stars.