Theoretical constraints on models with vector-like fermions

TL;DR

This paper derives theoretical constraints on models extending the Standard Model with vector-like fermions and scalars, focusing on vacuum stability, perturbativity, and unification, impacting phenomenological predictions.

Contribution

It provides a comprehensive analysis of stability, perturbativity, and unification constraints on vector-like fermion models, with implications for collider and cosmological phenomenology.

Findings

Strong parameter space constraints identified

Implications for double Higgs production analyzed

Effects on electroweak phase transition discussed

Abstract

We provide a set of theoretical constraints on models in which the Standard Model field content is extended by vector-like fermions and in some cases also by a real scalar singlet. Our approach is based on the study of electroweak vacuum stability, perturbativity of model couplings and gauge couplings unification with the use of renormalization group equations. We show that careful analysis of these issues leads to strong constraints on the parameter space of the considered models. This, in turn, has important implications for phenomenology, as we show using examples of the double Higgs boson production, electroweak precision observables, and the electroweak phase transition.