Minimal Inert Doublet Benchmark for Dark Matter and the Baryon Asymmetry

TL;DR

This paper proposes a minimal extension of the Inert Doublet Model with a CP-violating operator that can simultaneously explain dark matter and the baryon asymmetry of the universe through a multi-step electroweak phase transition.

Contribution

It introduces a minimal IDM extension with an effective CP-violating operator capable of accounting for both dark matter relic abundance and baryogenesis, serving as a benchmark for realistic SM extensions.

Findings

The extension can quantitatively explain dark matter and baryogenesis.

The model predicts lepton electric dipole moments at the two-loop level.

Enhanced mass splitting can improve electroweak phase transition strength.

Abstract

In this article we discuss a minimal extension of the Inert Doublet Model (IDM) with an effective $CP$-violating $D=6$ operator, involving the inert Higgs and weak gauge bosons, that can lift it to a fully realistic setup for creating the baryon asymmetry of the Universe (BAU). Avoiding the need to stick to an explicit completion, we investigate the potential of such an operator to give rise to the measured BAU during a multi-step electroweak phase transition (EWPhT) while sustaining a viable DM candidate in agreement with the measured relic abundance. We find that the explored extension of the IDM can account quantitatively for both DM and for baryogenesis and has quite unique virtues, as we will argue. It can thus serve as a benchmark for a minimal realistic extension of the SM that solves some of its shortcomings and could represent the low energy limit of a larger set of viable completions. After discussing the impact of a further class of operators that open the possibility for a larger mass splitting (enhancing the EWPhT) while generating the full relic abundance also for heavy inert-Higgs DM, we ultimately provide a quantitative evaluation of the induced lepton electric dipole moments in the minimal benchmark for the BAU. These arise here at the two-loop level and are therefore less problematic compared to the ones that emerge when inducing $CP$ violation via an operator involving the SM-like Higgs.