CP-violation and its implications in a complex singlet extension of 2HDM

Abstract

We investigate CP-violation in the complex singlet extension of the general Two Higgs Doublet Model (2HDM) with Yukawa alignment condition. We first explore the possibility of explicit CP-violation in the extended scalar sector while the 125 GeV Higgs remains exactly Standard Model (SM)-like. We identify an additional source of CP violation in the complex singlet extension compared to the 2HDM, which allows this model a substantially greater freedom in satisfying the stringent EDM constraints. We also incorporate dark matter in this model and investigate the impacts of constraints from the dark sector on the model parameter space and its interplay with CP-violation phases. We further explore the possibility of detecting such a scenario at future collider experiments via CP-violating trilinear couplings among the non-standard scalars. Finally, we also deviate from the exact alignment limit and investigate the CP-properties of the observed Higgs boson in the context of our model. We demonstrate the strong model-dependent nature of the detection prospects of the CP-phase of the Higgs boson at future experiments, exploring both fermion couplings as well as the trilinear self-coupling of the Higgs boson.

Figures (18)

• Figure 1: The two-loop Bar-Zee diagrams with fermion (left), scalar (middle) and gauge-boson (right) loop contributions. The solid lines with pointing arrows denote fermion lines (quarks and leptons), the dashed lines denote scalars ($H_{1..4}$ and $H^{\pm}$), and the wavy lines represent gauge bosons ($\gamma, Z, W$).
• Figure 2: Constraints on $\theta_{CP}$ from the most recent electron EDM bound with $\theta_7=0, \theta_f=0$, $|\lambda_7|=0.3, \lambda_2'=0$.
• Figure 3: Constraints on $\theta_{CP}$ and $\theta_7$ from the most recent electron EDM bound. $\theta_f=0$, $\lambda_7=0.3, \lambda_2'=0, \lambda_{5}'=1$, Masses of non-standard scalars $m_{H_i}\approx 200$ GeV. The electron EDM $|d_e|$ for the parameter points in units of $10^{-29}$ is shown in the color axis.
• Figure 4: (left) Electron-EDM allowed region in $\theta_u-\theta_7$ parameter space in Yukawa-aligned 2HDM with rest of the parameters given in Table \ref{['2hdminput']} (Figure borrowed from Kanemura:2020ibp). (right) In 2HDMS, electron-EDM allowed region in $\theta_u-\theta_7$ parameter space with inputs from Table \ref{['2hdminput']} and the additional relevant parameters are varied as follows: $-\pi < \theta_{CP} < \pi$ and $0 < \lambda_5' < 10$.
• Figure 5: The allowed region in CP-violating 2HDMS with $\left[\theta_u,\theta_7\right]=\left[\frac{\pi}{2},\frac{\pi}{2}\right]$, all other parameters kept fixed as in Table \ref{['2hdminput']}. The orange points correspond to $m_{H_4} = 200$ GeV, and the maroon points correspond to $m_{H_4}=700$ GeV.