Mechanism for baryogenesis via feebly interacting massive particles

TL;DR

This paper proposes a mechanism where out-of-equilibrium decays of heavy particles produce both dark matter via freeze-in and baryon asymmetry through CP violation, linking dark matter and baryogenesis.

Contribution

It introduces a unified scenario for baryogenesis and dark matter production using feebly interacting particles and illustrates it with a specific vectorlike fermion model.

Findings

Heavy fermions with TeV-scale masses satisfy cosmological constraints.

Dark matter is predicted to be a light keV-scale scalar.

Potential detectability at the High-Luminosity LHC.

Abstract

We present a simple mechanism which allows the simultaneous generation of the baryon asymmetry of the Universe along with its dark matter content. To this goal, we employ the out-of-equilibrium decays of heavy bath states into a feebly coupled dark matter particle and Standard Model charged fermions. These decays lead to dark matter production via the freeze-in mechanism and, assuming that they further violate $CP$, can generate a viable matter-antimatter asymmetry in the resonant regime. We illustrate this mechanism by studying a particular realization of this general scenario, where the role of the heavy bath particles is played by $SU(3)_{\text{c}}\times SU(2)_{\text{L}}$-singlet vectorlike fermions with a non-zero hypercharge and dark matter is identified with a gauge-singlet real scalar field. We show that in the context of this simple model the cosmological constraints for the dark matter abundance and the baryon asymmetry are satisfied for masses of heavy vectorlike fermion states of a few TeV, potentially within reach of the High-Luminosity Run of the Large Hadron Collider. Dark matter, in turn, is predicted to be rather light, with a mass of a few keV.