Speaker
Description
The nature of dark matter in our Universe remains one of the most compelling inquiries in fundamental physics today. While weakly interacting massive particles (WIMPs) have been the primary candidates for dark matter in the past decades, alternative explanations have gained more and more attention due to a growing number of null-results in experimental WIMP searches. Here, we go beyond the WIMP paradigm by considering very weakly dark matter couplings mediated by a t-channel mediator particle charged under SU(3)_c. In the early Universe, they can form bound states which largely alter the freeze-out dynamics. Interestingly, due to the small dark matter couplings, the freeze-out process is prolonged towards smaller temperatures, rendering higher excitations to become increasingly important due to their larger bound state formation cross section and multiplicity. We present an efficient way to include a large number of excited states (up to around a million) and investigate the scenario's phenomenology. The model allows for dark matter genesis via so-called conversion-driven freeze-out or superWIMP production. In the former mechanism, semi-efficient conversions between the colored mediator and dark matter initiate thermal freeze-out. In the latter scenario, late decays of the mediator particle into dark matter produce a non-thermal abundance. In both scenarios, we find that bound state effects play a key role in the relic density computation affecting the result by up to an order of magnitude with important phenomenological implications. The scenarios can be tested at the LHC through searches for long-lived particles as well as cosmological probes of the small scale structure, respectively.