Marieke Postma (Nikhef, Netherlands)
If dark matter couples directly to a light force mediator, then it may form bound states in the early universe and in the non-relativistic environment of haloes today. In this talk I will present a field-theoretic framework for the computation of bound-state formation cross-sections, de-excitation and decay rates, in theories with long-range interactions. At low relative velocities of the interacting particles, the formation of bound states is enhanced by the Sommerfeld effect. For scalar particle-antiparticle pairs, we show that bound-state formation can be faster than annihilation into radiation in the regime where the Sommerfeld effect is important.