Surveying the complex three Higgs doublet model with Machine Learning

TL;DR

This work extends the exploration of N-Higgs doublet models by performing a comprehensive ML-driven survey of the softly broken $ obreak\mathbb{Z}_2\times\mathbb{Z}_2$-symmetric three-Higgs-doublet model (C3HDM) with explicit CP violation. It analyzes five Yukawa Types and five neutral-scalar orderings, computing the scalar potential, Yukawa and gauge interactions, and imposing a broad set of theoretical and experimental constraints. Using an evolutionary strategy with novelty rewards, the authors identify viable regions where the 125 GeV Higgs, $h_{125}$, can have large CP-odd couplings to fermions, including scenarios where $h_{125}bb$ is purely CP-odd while $h_{125}tt$ remains CP-even, and vice versa. The results reveal that eight CP structures are compatible with current data across specific orderings, while the $h_{125}=h_5$ case is heavily disfavored in several Types, underscoring the continued importance of precise CP measurements (notably in $c^o_{tt}$ and $c^o_{ au au}$) for uncovering CP-violating Higgs dynamics.

Abstract

The couplings of the 125 GeV Higgs are being measured with higher precision as the Run 3 stage of LHC continues. Models with multiple Higgs doublets allow potential deviations from the SM predictions. For more than two doublets, there are five possible types of models that avoid flavor changing neutral couplings at tree level by the addition of a symmetry. We consider a softly broken Z2xZ2 three-Higgs doublet model with explicit CP violation in the scalar sector, exploring all five possible types of coupling choices and all five mass orderings of the neutral scalar bosons. The phenomenological study is performed using a Machine Learning black box optimization algorithm that efficiently searches for the possibility of large pseudoscalar Yukawa couplings. We identify the model choices that allow a purely pseudoscalar coupling in light of all recent experimental limits, including direct searches for CP-violation, thus motivating increased effort into improving the experimental precision.

Figures (12)

• Figure 1: Allowed regions in the charged scalar masses plane for the Type II model with the ordering $h_{125}=h_3$, including focused runs on the low charged scalar mass region.
• Figure 2: Allowed $h_{125}$-fermion coupling regions obtained in the Type I C3HDM for the possible orderings. The solid and dashed lines correspond to the limits on top-quark couplings from Ref. ATLAS:2020ior, including runs focused on the couplings shown.
• Figure 3: Allowed $h_{125}$-fermion coupling regions in Type II models for the different ordering choices, including runs focused on the couplings shown.
• Figure 4: Allowed $h_{125}$-fermion coupling regions in Type X models for the different ordering choices, including runs focused on the couplings shown.
• Figure 5: Allowed $h_{125}$-fermion coupling regions in Type Y models for the different ordering choices, including runs focused on the couplings shown.