Dark-matter spontaneous freeze out

Abstract

We consider the possibility that thermalized dark-matter particles acquire their mass thanks to the spontaneous breaking of a symmetry below some critical temperature. We describe the regime where a freeze out mechanism takes place shortly after the onset of the phase transition, while the dark-matter mass has not yet reached its final constant value. For such a "spontaneous freeze out" to yield the correct relic density, the present-time cross section of annihilation of the dark matter into Standard-Model states has to be one or two orders of magnitude larger than in the case of a constant dark-matter mass.

Comments: Based on a talk given at the International Conference on Neutrinos and Dark Matter (NDM-2020), 11-14 January 2020, Hurghada, Egypt