Resonant SIMP dark matter

Abstract

We consider a resonant SIMP dark matter in models with two singlet complex scalar fields charged under a local dark $U(1)_D$. After the $U(1)_D$ is broken down to a $Z_5$ discrete subgroup, the lighter scalar field becomes a SIMP dark matter which has the enhanced $3\rightarrow 2$ annihilation cross section near the resonance of the heavier scalar field. Bounds on the SIMP self-scattering cross section and the relic density can be fulfilled at the same time for perturbative couplings of SIMP. A small gauge kinetic mixing between the SM hypercharge and dark gauge bosons can be used to make SIMP dark matter in kinetic equilibrium with the SM during freeze-out.