Multi Component Dark Matter in a Minimal Model

TL;DR

This paper investigates a minimal multi-component dark matter model with two fermions and a scalar, analyzing their relic densities and detection prospects within a Higgs portal framework.

Contribution

It introduces a minimal model with three stable particles, exploring parameter regions compatible with observed dark matter abundance and detection constraints.

Findings

Scalar DM can evade current direct detection bounds.

Fermion DM's scattering cross section is loop suppressed and below the neutrino floor.

Viable parameter space exists with scalar DM contributing minimally to relic density.

Abstract

We study a minimal model with an imposed $\mathbb{Z}_2$ symmetry incorporating two singlet fermions and a singlet scalar which communicate with the SM particles through a scalar-Higgs portal. We probe regions in the parameter space where stability of the three new particles are guaranteed kinematically, and thus introducing a multi component dark matter (DM) scenario. The regions in the parameter space with predicted total relic density in accordance with the observed DM abundance are found, and the contribution of each species to the total relic density is determined. The elastic DM-nucleon scattering cross section of the two fermions DM are loop suppressed, while that of the scalar DM starts at tree level and thus presumably being dominant. It is found that there exist a viable region in the parameter space that the scalar DM can evade the current direct detection (DD) experimental bounds while it has a minimal contribution to the observed relic density. The DD cross section of the fermion DM being loop suppressed, resides below the lower limit from the {\it neutrino floor}, possessing a large fraction of the total relic density.