Minimal sterile neutrino dark matter
Torsten Bringmann, Paul Frederik Depta, Marco Hufnagel, Jörn Kersten, Joshua T. Ruderman, Kai Schmidt-Hoberg
Abstract
We propose a novel mechanism to generate sterile neutrinos ${\ensuremath{\nu}}_{s}$ in the early Universe, by converting ordinary neutrinos ${\ensuremath{\nu}}_{\ensuremath{\alpha}}$ in scattering processes ${\ensuremath{\nu}}_{s}{\ensuremath{\nu}}_{\ensuremath{\alpha}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{s}{\ensuremath{\nu}}_{s}$. After initial production by oscillations, this leads to an exponential growth in the ${\ensuremath{\nu}}_{s}$ abundance. We show that such a production regime naturally occurs for self-interacting ${\ensuremath{\nu}}_{s}$, and that this opens up significant new parameter space where ${\ensuremath{\nu}}_{s}$ make up all of the observed dark matter. Our results provide strong motivation to further push the sensitivity of X-ray line searches, and to improve on constraints from structure formation.