Theory HEP Seminar

Model independent constraints on warm hidden dark matter

Subinoy Das

RWTH Aachen

We explore the model-independent constraints from cosmology on a dark-matter particle with no prominent standard model interactions that interacts and thermalizes with other particles in a hidden sector. We characterize the relevant physics by the annihilation cross section, mass, and temperature ratio of the hidden to visible sectors. While encompassing the standard cold WIMP scenario, we do not require the freeze-out process to be nonrelativistic. Rather, freeze-out may also occur when dark matter particles are semirelativistic. This gives a possibility of warm dark matter as thermal relic in hidden sector. A keV sterile neutrino which is not in thermal contact with stanard model but thermalized in a dark sector, is a good example for this. We consider different cosmological constraints on such scenario and show that for warm dark matter masses <1.5 keV no region of parameter space satisfies all cosmological constraints. This is a gravitationally-mediated lower bound on the dark-matter mass for any model in which the primary component of dark matter once had efficient interactions -- even if it has never been in equilibrium with the standard model.