Observing the dark sector with supernovae

It has been long known that the excessive cooling of supernovae places strong limits on models of light dark sectors. However, even at couplings where the flux of new particles produced in a supernova is too low to violate the cooling bound, the flux remains large and can be observed through a variety of signatures, both direct and indirect. We analyze two different models with radically different behavior. The first model is that of a dark photon on the MeV scale. This model can be probed via the observation of electromagnetic signals produced in dark photon decay. The second model is that of a dark U(1) sector with heavy mediator and MeV-scale dark fermions. In this case, the flux emerging from supernovae is much hotter than the galactic dark matter, allowing it to be detected in existing direct detection experiments designed to hunt for GeV-scale dark matter. In both cases, we find that these signatures allow new bounds to be placed well outside existing cooling limits. Furthermore, these new signals may allow for a future discovery of the dark matter.