Speaker
Description
I explore the impact of highly excited bound states on the evolution of number densities of new physics particles, specifically dark matter, in the early Universe.
Higher excited states play a crucial role in non-Abelian interactions, going as far as preventing a complete decoupling in the early Universe and thus preventing the constituent particle from freezing out. Instead, a continuous depletion is driven by consecutive bound state formation and decay in the regime consistent with perturbativity and unitarity.
I will highlight how the mechanism has profound impact in a simplified dark matter model featuring a colored and electrically charged t-channel mediator. The focus is hereby on the regime of superWIMP production which is commonly characterized by a mediator freeze-out followed by its late decay into dark matter. In contrast, we find that excited states render mediator depletion efficient all the way until its decay, introducing a dependence of the dark matter density on the mediator lifetime as a novel feature. The impact of bound states on the viable dark matter mass can amount to an order of magnitude, relaxing constraints from Lyman-α observations.
