# Probing extra Yukawa couplings by precision measurements of Higgs properties

## TL;DR

This paper investigates how precision measurements of Higgs properties can reveal or constrain additional Yukawa couplings in general two Higgs doublet models, especially through loop effects on the $hZZ$ coupling.

## Contribution

It provides a one-loop calculation of the $hZZ$ coupling in the presence of extra Yukawa interactions, exploring their effects on Higgs precision measurements and bounds on new couplings.

## Key findings

- Future collider measurements can set stronger bounds on $
ho_{tt}$ than current flavor experiments.
- Cancellation effects can allow alignment without decoupling even with relatively light exotic scalars.
- The study identifies parameter regions where exotic Yukawa couplings significantly influence Higgs properties.

## Abstract

If one removes any \emph{ad hoc} symmetry assumptions, the general two Higgs doublet model should have additional Yukawa interactions independent from fermion mass generation, in general involving flavor changing neutral Higgs couplings. These extra couplings can affect the discovered Higgs boson $h$ through fermion loop contributions. We calculate the renormalized $hZZ$ coupling at one-loop level %by on-shell and minimal subtraction scheme, and evaluate the dependence on heavy Higgs boson mass and extra Yukawa coupling $\rho_{tt}$. Precision measurements at future colliders can explore the parameter space, and can give stronger bound on $\rho_{tt}$ than the current bound from flavor experiments. As a side result, we find that if $\rho_{tt}\cos\gamma < 0$, where $\cos\gamma$ is the exotic Higgs component of $h$, the $\rho_{tt}$-induced top loop contribution cancels against bosonic loop contributions, and one may have alignment without decoupling, namely $\sin(-\gamma) \simeq 1$, but exotic scalar bosons could have masses at several hundred GeV.