A Closer Look at CP-Violating Higgs Portal Dark Matter as a Candidate for the GCE

TL;DR

This paper investigates Majorana dark matter with CP-violating Higgs portal interactions as a potential explanation for the Galactic Center Excess, analyzing two minimal models and their experimental viability.

Contribution

It introduces and explores two minimal UV-complete models of CP-violating Higgs portal dark matter as candidates for the GCE, mapping their viable parameter spaces.

Findings

Certain parameter regions can explain the GCE while satisfying experimental constraints.

Large CP-violation can suppress scattering rates, making detection more challenging.

Models remain consistent with current collider and direct detection limits.

Abstract

A statistically significant excess of gamma rays has been reported and robustly confirmed in the Galactic Center over the past decade. Large local dark matter densities suggest that this Galactic Center Excess (GCE) may be attributable to new physics, and indeed it has been shown that this signal is well-modelled by annihilations dominantly into $b\bar{b}$ with a WIMP-scale cross section. In this paper, we consider Majorana dark matter annihilating through a Higgs portal as a candidate source for this signal, where a large CP-violation in the Higgs coupling may serve to severely suppress scattering rates. In particular, we explore the phenomenology of two minimal UV completions, a singlet-doublet model and a doublet-triplet model, and map out the available parameter space which can give a viable signal while respecting current experimental constraints.