Pseudo-Goldstone Dark Matter Model with CP violation

TL;DR

This paper introduces a CP-violating two-Higgs-doublet model with a complex singlet scalar, where the imaginary part of the singlet acts as a stable dark matter candidate, satisfying detection constraints and allowing for relic abundance and indirect detection analysis.

Contribution

It presents a novel CP-violating framework with a complex singlet scalar that naturally decouples from nucleons, contrasting with traditional models, and explores its dark matter phenomenology.

Findings

Dark matter candidate decouples from nucleons at tree level.

CP violation persists in the alignment limit of the model.

Relic abundance and indirect detection prospects are analyzed.

Abstract

We consider an explicitly CP-violating model with two Higgs doublets and one complex singlet scalar. The singlet $S$ is charged under a global $\rm U(1)$ symmetry which is softly broken by a mass term $\mu^2 S^2+\hc$. Imaginary part of $S$ is a stable dark matter candidate which at the tree level, in the limit of zero momentum transfer, decouples from nucleons naturally satisfying all existing direct detection limits on dark matter scattering cross-section. It is explicitly shown that within this framework in the alignment limit CP-violation is still present in contrast to a popular version of a 2-Higgs doublet model with softly broken $Z_2$ symmetry. In this context, we investigate dark matter implications of the model both with and without CP violation in the scalar sector. In particular, dark matter relic abundance is calculated and the possibility for its indirect detection is discussed.