Road map through the desert with scalars

TL;DR

This paper systematically analyzes extensions of the Standard Model with vector-like fermions and scalars to achieve gauge coupling unification, deriving bounds on new particle masses and assessing future experimental prospects.

Contribution

It identifies 145 viable models with new particles that satisfy unification, providing mass bounds and exploring their testability at future colliders and proton decay experiments.

Findings

145 models satisfy unification conditions

Lower bounds on exotic particle masses derived

Many models already constrained or testable in upcoming experiments

Abstract

In the context of the gauge coupling unification, we present a comprehensive analysis of the extensions of the Standard Model with vector-like fermions and scalars. We find 145 models that satisfy the unification condition, which are distinguishable by the number of new particles in the spectrum and by their transformation properties under the gauge symmetry group of the Standard Model. For all models we derive lower bounds on the exotic fermion and scalar masses, stemming from the measurement of the strong gauge coupling scale dependence, from the heavy stable charged particle searches, and from the electroweak precision tests. We also discuss the potential of testing the unification scenarios at the future 100 TeV collider and in the proton decay experiments. We show that many models can already be excluded based on the current data, while many others will be entirely probed in the coming years.