Speaker
Description
In many theoretical models, the observed matter-antimatter asymmetry originates from out-of-equilibrium decays and scatterings of heavy particles. In these scenarios, charge-parity (CP) symmetry violation arises perturbatively through the interference between tree-level and one-loop diagrams. As a result, the CP asymmetry, characterized by the parameter $\epsilon$, is suppresed by higher orders in couplings due to the presence of a loop. Remarkably, unitarity places no direct constraint on $\epsilon$, implying that it could, in principle, be of order one. In this talk, I will show that scatterings mediated by force carriers much lighter than the interacting particles can indeed produce order-one CP asymmetries, even for arbitrarily small couplings. Furthermore, I will demonstrate that in such cases, the rate of CP-violating scatterings saturates the partial-wave unitarity bound.
