Constraints on realistic Gauge-Higgs unified models

TL;DR

This paper analyzes the structure of gauge-Higgs unified models, identifying conditions for models to include quarks and have a zero oblique T-parameter, and discusses the challenge of achieving the correct weak-mixing angle.

Contribution

It characterizes the group structures of gauge-Higgs models, identifying special cases with light vectors and analyzing their phenomenological viability.

Findings

Most models imply additional light vectors beyond the Standard Model

Models accommodating quarks with zero T-parameter cannot have | ext{sw}| \, \sim 1/2 at tree-level

The weak-mixing angle problem remains unresolved in these models

Abstract

We investigate the general group structure of gauge-Higgs unified models. We find that a given embedding of the \sm\ gauge group will imply the presence of additional light vectors, except for a small set of special cases, which we determine; the arguments presented are independent of the compactification scheme. For this set of models we then find those that can both accommodate quarks and have a vanishing oblique T-parameter at tree-level. We show that none of the resulting models can have $|\sw| \sim1/2 $ (the sine of the weak-mixing angle) at tree-level and briefly discuss possible solutions to this problem.