Electroweak interacting dark matter with a singlet scalar portal

TL;DR

This paper explores a model of electroweak dark matter interacting via a singlet scalar portal, analyzing CP violation effects, electron EDM constraints, and direct detection prospects.

Contribution

It introduces a novel electroweak dark matter model with CP violation through a singlet scalar portal, examining experimental constraints and detection prospects.

Findings

Current electron EDM bounds do not exclude wide parameter space due to cancellation effects.

Residual higher-order effects yield an O(10^{-47}) cm^2 spin-independent cross section.

Future experiments can fully test the proposed model.

Abstract

We investigate an electroweak interacting dark matter (DM) model in which the DM is the neutral component of the SU$(2)_L$ triplet fermion that couples to the standard model (SM) Higgs sector via an SM singlet Higgs boson. In this setup, the DM can have a CP-violating coupling to the singlet Higgs boson at the renormalizable level. As long as the nonzero Higgs portal coupling (singlet-doublet Higgs boson mixing) exists, we can probe CP violation of the DM via the electric dipole moment of the electron. Assuming the $\mathcal{O}(1)$ CP-violating phase in magnitude, we investigate the relationship between the electron EDM and the singlet-like Higgs boson mass and coupling. It is found that for moderate values of the Higgs portal couplings, current experimental EDM bound is not able to exclude the wide parameter space due to a cancellation mechanism at work. We also study the spin-independent cross section of the DM in this model. It is found that although a similar cancellation mechanism may diminish the leading-order correction, as often occurs in the ordinary Higgs portal DM scenarios, the residual higher-order effects leave an $\mathcal{O}(10^{-47})~{\rm cm}^2$ correction in the cancellation region. It is shown that our benchmark scenarios would be fully tested by combining all future experiments of the electron EDM, DM direct detection and Higgs physics.