The High Quality QCD Axion and the LHC

TL;DR

This paper explores a robust high-quality QCD axion model with a mirror sector, highlighting its potential to be detected as a long-lived particle at the LHC through distinctive hadronic decay signals.

Contribution

It introduces a mirror sector-based axion model that remains viable under constraints and proposes a novel collider detection strategy for long-lived axions at the LHC.

Findings

The heavy axion can be produced at the LHC with detectable signals.

The axion's decay signature can be distinguished from background.

The model opens new avenues for collider searches of axions and LLPs.

Abstract

The QCD axion provides an elegant solution to the Strong CP Problem. While the minimal realization is vulnerable to the so-called "Axion Quality Problem", we will consider a more robust realization in the presence of a mirror sector related to the Standard Model by a (softly broken) $\mathbb{Z}_2$ symmetry. We point out that the resulting "heavy" axion, while satisfying all theoretical and observational constraints, has a large and uncharted parameter space which allows it to be probed at the LHC as a Long-Lived Particle (LLP). The small defining axionic coupling to gluons results in a challenging hadronic decay signal which we argue can be distinguished against the background in such a long-lived regime, and yet, the same coupling allows for sufficient production at hadron colliders thanks to the large gluon parton luminosity. Our study opens up a new window towards accelerator observable axions, and more generally, singly produced LLPs.