Resonant s-channel dark matter annihilation at NLO

A bstract Studies of dark matter annihilation through an s -channel resonance are often based on recipes such as a narrow width approximation or real intermediate state subtraction. We review recipe-free formalism that can be implemented at the NLO level in full theory, and ensures cancellation mass singularities. Its basic ingredients formulated relativistic regime, but we show procedure simplifies if go to non-relativistic one assume presence kinetic equilibrium. The latter case is illustrated for scalar singlet with m φ ≃ 60 GeV, freezing out T (1–3) re-confirming viability this scenario couplings tiny enough evade experimental constraints.