The Price of a Large Electron Yukawa Modification

TL;DR

This paper explores the theoretical and phenomenological implications of modifying the electron Yukawa coupling, focusing on potential bounds from future collider experiments and the associated fine-tuning issues.

Contribution

It provides a comprehensive analysis of the effects of electron Yukawa modifications within effective field theory and simplified models, including renormalisation effects and phenomenological constraints.

Findings

Renormalisation group effects influence related observables.

Constraints on Yukawa modifications depend on UV flavor assumptions.

Fine-tuning considerations are significant in model viability.

Abstract

The theoretical implications of an electron Yukawa modification are considered in the context of a possible Higgs pole run at FCC-ee, aimed at bounding this coupling. We start from an effective field theory viewpoint, considering the impact of renormalisation group effects on related observables and also examining assumptions on the broader UV flavour structure. We then give an overview of the landscape of simplified models, investigating phenomenological constraints arising at higher orders. A short discussion of fine-tuning is also included.