Axionlike electrophilic portal for pion dark matter

We investigate a scenario where strongly interacting massive particle (SIMP) dark matter interacts with an axionlike particle (ALP) that couples exclusively to electrons. This minimal setup provides interactions which enforce thermal equilibrium between dark matter and the standard model (SM) in the early Universe. We analyze the cosmological evolution of the dark sector and the constraints arising from dark matter annihilations, ALP laboratory searches and astrophysical observations. Our results show that the allowed parameter space is wider than previous studies and an ALP with mass m a ∼ O ( 10 ) MeV can act as a viable portal between the visible and dark sectors. Interestingly, this mass range overlaps with the parameter space suggested by the reported X 17 anomaly. Furthermore, the introduction of nonvanishing θ angle in the dark sector of the model opens up the parameter space to heavy ALP masses.