Are Low-energy Data already Hinting at Five Dimensions?

TL;DR

This paper explores how low-energy data, especially Higgs and top quark measurements, suggest a five-dimensional gauge-Higgs unification model, predicting new vector-like fermions and specific energy scales.

Contribution

It proposes a 5D GHU model that links the Higgs quartic coupling, top Yukawa, and gauge couplings, and predicts vector-like fermions and compactification scales.

Findings

Higgs quartic coupling vanishes at high scale

Top Yukawa and gauge couplings unify in the model

Predicted vector-like fermion masses and compactification scale

Abstract

Low-energy data, combined with renormalization group (RG) equations, can predict new physics at far higher energy scales. In this paper, we consider the possibility that the measured Higgs boson mass and top quark mass hint at a five-dimensional gauge-Higgs unification (5D GHU) model at a scale above TeV. We note that the vanishing of the Higgs quartic coupling and the proximity of the top quark Yukawa coupling and weak gauge coupling at high scales, inferred from the experimental data, are in harmony with 5D GHU, because in 5D GHU models the Higgs quartic coupling is forbidden by the 5D gauge symmetry and the Yukawa couplings and the weak gauge coupling originate from a common 5D gauge coupling. Based on the above insight, we propose a 5D GHU model where the Standard Model fermions are embedded in 5D fermions in a way to tightly relate the top Yukawa coupling with the weak gauge coupling. Also, the model predicts the presence of vector-like fermions (other than the Kaluza-Klein modes), which can affect the RG evolutions of the 4D theory and reconcile the scale of vanishing Higgs quartic coupling and that of equality of the top Yukawa and weak gauge couplings, thereby achieving a successful matching of the 4D theory with 5D GHU. We predict the vector-like fermion mass and the compactification scale of 5D GHU from the conditions for the successful matching.