Large pseudoscalar Yukawa couplings in the complex 3HDM

TL;DR

This paper explores the potential for large pseudoscalar Yukawa couplings in a complex three Higgs doublet model, revealing that certain CP-violating coupling configurations remain viable and warrant further experimental investigation.

Contribution

It demonstrates that a three Higgs doublet model with explicit CP violation can still accommodate large pseudoscalar Yukawa couplings, unlike simpler models that are now constrained by recent data.

Findings

Curious CP-even/CP-odd top/bottom coupling scenario is partly revived in C3HDM.

Full 2024 experimental data rules out some previous coupling configurations.

Further experimental tests are needed to explore these couplings.

Abstract

As LHC's Run3 unfolds, we peer deeper into the couplings of the 125GeV Higgs ($h_{125}$) and also test for extra scalars. Even before such extra scalars are found, one can probe them by using the fact that theories with multiple Higgs doublets allow for substantial deviations of the couplings of $h_{125}$ from their SM values. Indeed, the observed couplings already place stringent limits on such theories. We investigate the curious possibility that $h_{125}$ couples to the top quark mostly as a scalar, while it couples to the bottom quark mostly as a pseudoscalar. This possibility was allowed by 2017 data for the so-called C2HDM; a two Higgs doublet model with a single source of explicit CP violation. It was shown recently that this possibility disappears when using the full experimental data of 2024. Here we discuss a three Higgs doublet with explicit CP violation (C3HDM), and show that the curious CP-even/CP-odd $t$/$b$ possibility is partly resuscitated, prompting further experimental exploration of this prospect.