Two Higgs doublets, a 4th generation and a 125 GeV Higgs: a review

TL;DR

This review explores how two-Higgs-doublet models could explain the behavior of a hypothetical heavy 4th generation of fermions, considering experimental constraints and recent Higgs discoveries.

Contribution

It provides a comprehensive overview of multi-Higgs models with a 4th fermion generation, highlighting their phenomenological implications and experimental constraints.

Findings

Compatibility with a 125 GeV Higgs observed at LHC

Constraints from electroweak precision data and flavor physics

Implications for collider searches of Higgs and 4th generation fermions

Abstract

We review the possible role that multi-Higgs models may play in our understanding of the dynamics of a heavy 4th sequential generation of fermions. We describe the underlying ingredients of such models, focusing on two Higgs doublets, and discuss how they may effectively accommodate the low energy phenomenology of such new heavy fermionic degrees of freedom. We also discuss the constraints on these models from precision electroweak data as well as from flavor physics and the implications for collider searches of the Higgs particles and of the 4th generation fermions, bearing in mind the recent observation of a light Higgs with a mass of ~125 GeV.