Dark Matter and Baryogenesis from Visible-Sector Long-Lived Particles

Abstract

We present a minimal extension of the standard model that includes a long-lived fermion with weak-scale mass and an $\mathcal{O}(\mathrm{GeV})$ fermionic dark matter candidate both of which are coupled to quarks. Decays of a TeV-scale colored scalar in a radiation-dominated phase bring the former to a thermal abundance while also producing dark matter. The long-lived fermion then dominates the energy density of the Universe and drives a period of early matter domination. It decays to reheat the Universe, mainly through baryon-number-violating interactions that also generate a baryon asymmetry, with a small branching fraction to dark matter. We find the allowed parameter space of the model and show that it can be probed by proposed long-lived particle searches as well as next-generation neutron-antineutron oscillation experiments. This model provides a robust explanation of dark matter and baryogenesis as long as the Universe is in a radiation-dominated phase at $T\gtrsim \mathcal{O}(\mathrm{TeV})$.

12 pages, 4 figures; updated to match published version

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