"Theory of Particle Physics and Cosmology" Seminar

Strongly Interacting Massive Particles (SIMPs) are a well-motivated DM candidate. SIMPs arise in dark QCD-like sectors, where the DM candidate is a dark pion. Usual SIMP models predict a constant cross section, which cluster bounds exclude. In Ref[2405.10367], it has been found that a non-vanishing theta angle would trigger resonant processes which would give rise to the observed relic density, together with providing velocity-dependent self-interactions without a light mediator. In this talk, I will present a particular realisation of this framework, focusing on a dark photon portal, discussing the thermalisation of the dark pions and the issues related to their stability. In the scenario we considered, a dark pion mass in the window of 10-50 MeV would be consistent with bounds from colliders, indirect detection, and the CMB, and it predicts resonant self-interactions. Finally, I will briefly discuss some astrophysical consequences of this model.