Improving Fermion Mass Hierarchy in Grand Gauge-Higgs Unification with Localized Gauge Kinetic Terms

TL;DR

This paper explores a five-dimensional SU(6) gauge theory with localized gauge kinetic terms to improve fermion mass hierarchy and achieve the observed Higgs boson mass within a grand gauge-Higgs unification framework.

Contribution

It introduces localized gauge kinetic terms in a 5D SU(6) model, enabling realistic fermion masses and Higgs mass without severe tuning, and analyzes their impact on gauge coupling and electroweak symmetry breaking.

Findings

Successfully reproduces SM fermion masses including top quark.

Achieves the observed 125 GeV Higgs boson mass.

Enhances the compactification scale to support Higgs mass.

Abstract

Grand gauge-Higgs unification of five dimensional SU(6) gauge theory on an orbifold S^1/Z_2 with localized gauge kinetic terms is discussed. The Standard model (SM) fermions on one of the boundaries and some massive bulk fermions coupling to the SM fermions on the boundary are introduced, so that they respect an SU(5) symmetry structure. The SM fermion masses including top quark are reproduced by mild tuning the bulk masses and parameters of the localized gauge kinetic terms. Gauge coupling universality is not guaranteed by the presence of the localized gauge kinetic terms and it severely constrains the Higgs vacuum expectation value. Higgs potential analysis shows that the electroweak symmetry breaking occurs by introducing additional bulk fermions in simplified representations.The localized gauge kinetic terms enhance the magnitude of the compactification scale, which helps Higgs boson mass large. Indeed the observed Higgs boson mass 125 GeV is obtained.