Chiral Asymmetry from a 5D Higgs Mechanism

TL;DR

This paper explores how a 5D Higgs mechanism can naturally produce chiral asymmetry in gauge theories, providing insights into the Standard Model's properties and discussing challenges in developing realistic models.

Contribution

It introduces a toy model demonstrating the emergence of chiral asymmetry from higher-dimensional theories via a 5D Higgs mechanism, highlighting potential explanations for Standard Model features.

Findings

Chiral asymmetry can arise naturally in 5D models with a Higgs mechanism.

The low-energy effective theory exhibits small gauge non-invariance effects.

Chiral asymmetry and gauge invariance are restored in the unbroken limit.

Abstract

An intriguing feature of the Standard Model is that the representations of the unbroken gauge symmetries are vector-like whereas those of the spontaneously broken gauge symmetries are chiral. Here we provide a toy model which shows that a natural explanation of this property could emerge in higher dimensional field theories and discuss the difficulties that arise in the attempt to construct a realistic theory. An interesting aspect of this type of models is that the 4D low energy effective theory is not generically gauge invariant. However, the non-invariant contributions to the observable quantities are very small, of the order of the square of the ratio between the light particle mass scale and the Kaluza-Klein mass scale. Remarkably, when we take the unbroken limit both the chiral asymmetry and the non-invariant terms disappear.