# Constraints from Triple Gauge Couplings on Vectorlike Leptons

## TL;DR

This paper investigates how future collider experiments can detect effects of vectorlike leptons on triple gauge couplings, potentially surpassing traditional precision tests in constraining new physics models.

## Contribution

It provides a detailed analysis of the sensitivity of FCC-ee, ILC, and CLIC to vectorlike leptons through triple gauge coupling measurements, highlighting their potential to outperform existing constraints.

## Key findings

- Future colliders can constrain vectorlike leptons more effectively than oblique parameters.
- Measurements at different energies improve sensitivity to Higgs-coupled vectorlike fermions.
- Triple gauge couplings could serve as a new precision probe for new physics models.

## Abstract

We study the contributions of colorless vectorlike fermions to the triple gauge couplings $W^+ W^- \gamma$ and $W^+ W^- Z^0$. We consider models in which their coupling to the Standard Model Higgs boson is allowed or forbidden by quantum numbers. We assess the sensitivity of the future accelerators FCC-ee, ILC and CLIC to the parameters of these models, assuming they will be able to constrain the anomalous triple gauge couplings with a precision $\delta \kappa_V \sim \mathcal{O}(10^{-4})$, $V=\gamma,Z^0$. We show that the combination of measurements at different center-of-mass energies helps to improve the sensitivity to the contribution of vectorlike fermions, in particular when they couple to the Higgs. In fact, the measurements at the FCC-ee and, especially, the ILC and the CLIC, may turn the triple gauge couplings into a new set of precision parameters able to constrain the models better than the oblique parameters or the $H \to \gamma \gamma$ decay, even assuming the considerable improvement of the latter measurements achievable at the new machines.