Discovering supernova-produced dark matter with directional detectors

Supernovae can produce vast fluxes of new particles with masses on the MeVscale, a mass scale of interest for models of light dark matter. When these newparticles become diffusively trapped within the supernova, the escaping fluxwill emerge semirelativistic with an order-one spread in velocities. As aresult, overlapping emissions from Galactic supernovae will produce an overallflux of these particles at Earth that is approximately constant in time.However, this flux is highly anisotropic and is steeply peaked towards theGalactic center. This is in contrast with the cosmological abundance of aWIMP-like dark matter which, due to the rotation of the Galaxy, appears to comefrom the direction of the Cygnus constellation. In this paper, we demonstratethe need for a directional detector to efficiently discriminate between asignal from a cold cosmological abundance of GeV-scale WIMPs and a signal froma hot population of supernova-produced MeV-scale dark matter.