Spontaneous baryogenesis from extremely light asymmetric dark matter

We present a mechanism where a particle asymmetry in one sector is used to generate an asymmetry in another sector. The two sectors are not coupled through particle number violating interactions and are not required to be in thermal contact with each other. When this mechanism is applied to baryogenesis in asymmetric dark matter models, we find that the dark matter particles can be extremely light, e.g. much lighter than an eV, and that in some cases there is no need to annihilate away the symmetric component of dark matter. We discuss a concrete realization of the mechanism with signals in direct detection, at the LHC, at $B$-factories, or in future beam dump experiments.

Figure 1

A diagrammatic picture of our toy model. The visible sector consists of a single fermion $\psi$ and an interaction that breaks the $\psi$ number. The dark sector consists of a single classical field $\varphi$ which carries an asymmetry. These two sectors communicate through a single higher dimensional current-current interaction.

Figure 2

Dark matter–nucleon scattering cross section as a function of dark matter mass (light blue line). The purple dashed line shows the projected reach of SuperCDMS SNOLAB [56].