Two-Higgs-Doublet type-II and -III models and $t\to c h$ at the LHC

TL;DR

This paper analyzes the constraints and phenomenology of the two-Higgs-doublet models type-II and type-III, focusing on Yukawa couplings, parameter correlations, and top-quark flavor-changing processes at the LHC.

Contribution

It provides a comprehensive fit of the 2HDM type-III parameters considering experimental and theoretical constraints, highlighting differences from type-II and implications for top FCNC decays.

Findings

Allowed parameter regions vary with $ aneta$ and $eta- ext{alpha}$.

Deviations in $h o Z ext{gamma}$ can reach about 10%.

Branching ratios for $t o c(h, H)$ are below $10^{-3}$, with some slightly exceeding this threshold.

Abstract

We study the constraints of the generic two-Higgs-doublet model (2HDM) type-III and the impacts of the new Yukawa couplings. For comparisons, we revisit the analysis in the 2HDM type-II. To understand the influence of all involving free parameters and to realize their correlations, we employ $\chi$-square fitting approach by including theoretical and experimental constraints, such as S, T, and U oblique parameters, the production of standard model Higgs and its decay to $\gamma\gamma$, $WW^*/ZZ^*$, $\tau^+\tau^-$, etc. The errors of analysis are taken at $68\%$, $95.5\%$, and $99.7\%$ confidence levels. Due to the new Yukawa couplings being associated with $\cos(\beta-\alpha)$ and $\sin(\beta -\alpha)$, we find that the allowed regions for $\sin\alpha$ and $\tan\beta$ in the type-III model can be broader when the dictated parameter $\chi_F$ is positive; however, for negative $\chi_F$, the limits are stricter than those in the type-II model. By using the constrained parameters, we find that the deviation from the SM in the $h\to Z\gamma$ can be of ${\cal O}(10\%)$. Additionally, we also study the top-quark flavor-changing processes induced at the tree level in the type-III model and find that when all current experimental data are considered, we get $Br(t\to c(h, H) )< 10^{-3}$ for $m_h=125.36$ and $m_H=150$ GeV and $Br(t\to cA)$ slightly exceeds $10^{-3}$ for $m_A =130$ GeV.