Sterile Neutrino Dark Matter

[摘要] After reviewing the relevant background in cosmology and dark matter physics, we show that active neutrino masses and a keV-GeV mass sterile neutrino dark matter candidate can result from a modified, low energy see-saw mechanism if right-handed neutrinos are charged under a new symmetry broken by a scalar field vacuum expectation value at the PeV scale. The dark matter relic abundance can be obtained through active-sterile oscillations or freeze-in through its interactions with this scalar field. We focus on the observable cosmological aspects of sterile neutrino dark matter produced via the freeze-in mechanism. The study is performed in a framework that admits many cosmologically interesting variations: high temperature production via annihilation processes from higher dimensional operators or low temperature production from decays of a scalar, with the decaying scalar in or out of equilibrium with the thermal bath, in supersymmetric or non-supersymmetric setups, thus allowing us to both extract generic properties and highlight features unique to particular variations. We find that while such sterile neutrinos are generally compatible with all cosmological constraints, interesting scenarios can arise where dark matter is cold, warm, or hot, has nontrivial momentum distributions, or provides contributions to the effective number of relativistic degrees of freedom during Big Bang nucleosynthesis large enough to be probed by future measurements. We also connect our model to two recent observations: PeV energy neutrinos at IceCube and a 3.5 keV X-ray line in the spectra of several galaxies. One or both of these observations can be explained within an extended supersymmetric neutrino sector. The same symmetry under which the sterile neutrinos are charged can sufficiently stabilize an additional PeV particle, produce its abundance through the freeze-in mechanism, and lead to decays that can give the energetic neutrinos observed by IceCube. The lightest sterile neutrino, if at 7 keV, is a non-resonantly produced fraction of dark matter, and can account for the 3.5 keV X-ray line. This framework naturally provides a sterile neutrino dark matter candidate with several possibilities for its production with interesting cosmological and astrophysical signatures.

[发布机构] University of Michigan

[效力级别] Neutrinos

[关键词] Dark Matter;Neutrinos;Physics;Science;Physics