Supersizing axions with small size instantons

TL;DR

This paper introduces a new method to calculate axion mass enhancements from small size instantons in models with extended color gauge symmetry, revealing potential collider signatures for heavy axions.

Contribution

It develops an explicit framework for evaluating instanton effects on axion properties, providing more precise predictions for axion masses and couplings in extended gauge models.

Findings

Axions can have electroweak scale or higher masses due to SSI effects.

Enhanced axion-meson mixing impacts collider phenomenology.

Potential for resonance searches at the LHC for heavy axions.

Abstract

We construct a new framework to calculate the enhancement of axion masses and concomitant effects on axion-meson mixing arising from small size instantons (SSIs), which originate in models featuring an extended color gauge symmetry. The framework is based on an explicit evaluation of 't Hooft determinantal operators that partition into instanton amplitudes, affording a more precise determination of the axion-diphoton coupling than previous results. Using an explicit model first presented in Ref. arXiv:1805.06465, we demonstrate that axions solving the strong CP problem can have electroweak scale masses and higher, driven by SSI effects. Such collider axions are prime targets for resonance searches at the Large Hadron Collider and afford a unique anchor for motivating extended color symmetries.