High Quality QCD Axion in the Standard Model

TL;DR

This paper proposes a minimal Standard Model extension with a discrete gauge symmetry that naturally produces a high-quality QCD axion, addressing the strong CP problem while also explaining neutrino masses, baryon asymmetry, and dark matter.

Contribution

It introduces a discrete gauge symmetry framework that naturally generates a high-quality axion and accounts for multiple fundamental phenomena within the Standard Model.

Findings

Predicts a testable parameter space for the axion.

Provides a unified explanation for neutrino masses, baryon asymmetry, and dark matter.

Addresses the axion quality problem without fine-tuning.

Abstract

Although the axion is the most compelling solution to the strong CP problem, the ad hoc introduced global Peccei-Quinn symmetry suffers from a severe fine-tuning problem known as the quality problem. In this Letter, we show that the discrete gauge symmetry $\mathbb Z_4 \times \mathbb Z_3$ motivated from the internal structure of the Standard Model can naturally predict a high-quality axion, leading to a distinct and testable parameter space. Remarkably, this minimal framework simultaneously accounts for neutrino masses, baryon asymmetry, and dark matter.