Dark Matter from Split Seesaw

TL;DR

This paper explores how the split seesaw mechanism in extra-dimensional models can naturally generate small neutrino masses and provide a dark matter candidate in the form of a keV-scale sterile neutrino, explaining cosmological observations.

Contribution

It demonstrates that the split seesaw framework can simultaneously account for neutrino masses, matter-antimatter asymmetry, and dark matter with a keV-scale sterile neutrino.

Findings

Sterile neutrino with ~5 keV mass fits X-ray data.

Split seesaw explains small neutrino masses naturally.

Dark matter candidate accounts for pulsar velocities.

Abstract

The seesaw mechanism in models with extra dimensions is shown to be generically consistent with a broad range of Majorana masses. The resulting democracy of scales implies that the seesaw mechanism can naturally explain the smallness of neutrino masses for an arbitrarily small right-handed neutrino mass. If the scales of the seesaw parameters are split, with two right-handed neutrinos at a high scale and one at a keV scale, one can explain the matter-antimatter asymmetry of the universe, as well as dark matter. The dark matter candidate, a sterile right-handed neutrino with mass of several keV, can account for the observed pulsar velocities and for the recent data from Chandra X-ray Observatory, which suggest the existence of a 5 keV sterile right-handed neutrino.