Protecting the Axion with Local Baryon Number

TL;DR

This paper proposes that gauging baryon number can naturally protect the Peccei-Quinn symmetry from Planck-scale violations, ensuring the viability of the axion solution to the Strong CP Problem.

Contribution

It introduces a novel mechanism where gauging baryon number provides automatic protection for the PQ symmetry using exotic fermions for anomaly cancellation.

Findings

Gauging baryon number can safeguard the PQ symmetry from Planck-scale operators.

Exotic fermions for anomaly cancellation can implement the hidden axion mechanism.

The approach offers a natural solution to the Strong CP Problem.

Abstract

The Peccei-Quinn (PQ) solution to the Strong CP Problem is expected to fail unless the global symmetry U(1)${}_{\rm PQ}$ is protected from Planck-scale operators up to high mass dimension. Suitable protection can be achieved if the PQ symmetry is an automatic consequence of some gauge symmetry. We highlight that if baryon number is promoted to a gauge symmetry, the exotic fermions needed for anomaly cancellation can elegantly provide an implementation of the Kim-Shifman-Vainshtein-Zakharov 'hidden axion' mechanism with a PQ symmetry protected from Planck-scale physics.