# Radiative Light Dark Matter

## TL;DR

This paper proposes a PQ-symmetric two-Higgs doublet model that naturally produces a light fermionic dark matter candidate through radiative mechanisms, with potential implications for cosmology and collider physics.

## Contribution

It introduces a novel radiative mechanism for generating light fermionic dark matter within a PQ-symmetric two-Higgs doublet framework, connecting dark matter, the strong CP problem, and collider phenomenology.

## Key findings

- Dark matter mass generated at one-loop level.
- Dark matter produced via freeze-in mechanism.
- Model has implications for LHC phenomenology.

## Abstract

We present a Peccei-Quinn (PQ)-symmetric two-Higgs doublet model that naturally predicts a fermionic singlet dark matter in the mass range 10 keV-1 GeV. The origin of the smallness of the mass of this light singlet fermion arises predominantly at the one-loop level, upon soft or spontaneous breakdown of the PQ symmetry via a complex scalar field in a fashion similar to the so-called Dine-Fischler-Sredniki-Zhitnitsky axion model. The mass generation of this fermionic Radiative Light Dark Matter (RLDM) requires the existence of two heavy vector-like SU(2) isodoublets, which are not charged under the PQ symmetry. We show how the RLDM can be produced via the freeze-in mechanism, thus accounting for the missing matter in the Universe. Finally, we briefly discuss possible theoretical and phenomenological implications of the RLDM model for the strong CP problem and the CERN Large Hadron Collider (LHC).