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

TL;DR

This paper proposes a minimal extension to the Standard Model introducing a long-lived fermion and a GeV-scale dark matter candidate, explaining dark matter and baryogenesis through early Universe dynamics involving a TeV-scale scalar.

Contribution

It introduces a new model linking dark matter and baryogenesis via long-lived particles and early matter domination, with testable predictions for future experiments.

Findings

Identifies parameter space consistent with observations.

Proposes experimental probes via long-lived particle searches.

Connects baryon asymmetry generation to dark matter production.

Abstract

We present a minimal extension of the standard model that includes a long-lived fermion with weak-scale mass and an ${\cal O}({\rm GeV})$ 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 $T \gtrsim {\cal O}({\rm TeV})$.