Light Dark Matter: Theoretical Motivation and Experimental Prospects

In most model building, the problems of dark matter (DM) and baryogenesis are treated separately. However, the similar magnitude of their observed abundances may be an indication of a common origin in the early universe. Models in which the DM carries a particle-antiparticle asymmetry can relate these two abundances. In contrast to WIMP miracle arguments, asymmetric models prefer DM masses around 1-10 GeV. With indirect annihilation signals suppressed, collider and direct detection searches offer the best opportunities for discovery. We will see that missing energy events at the LHC and Tevatron with a single jet do not yet rule out light WIMPs. Moreover, such mono-jet events can be easily faked by new physics involving neutrinos. On the other hand, upcoming low-threshold direct detection experiments, such as the Majorana Demonstrator, can collect hundreds to thousands of light WIMP scattering events. Despite this, we find that an accurate mass determination for light WIMPs will not be possible without an improved understanding of the local DM velocity distribution.