Phenomenology of the companion-axion model: photon couplings

Zhe Chen; Archil Kobakhidze; Ciaran A. J. O’Hare; Zachary S. C. Picker; Giovanni Pierobon

doi:10.1140/epjc/s10052-022-10909-6

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Particles and Fields

Open Access

Eur. Phys. J. C (2022) 82: 940
https://doi.org/10.1140/epjc/s10052-022-10909-6

Regular Article - Theoretical Physics

Phenomenology of the companion-axion model: photon couplings

Zhe Chen¹, Archil Kobakhidze¹, Ciaran A. J. O’Hare², Zachary S. C. Picker² and Giovanni Pierobon³^e

¹ Sydney Consortium for Particle Physics and Cosmology, School of Physics, The University of Sydney, 2006, Sydney, NSW, Australia
² School of Physics, The University of Sydney and ARC Centre of Excellence for Dark Matter Particle Physics, 2006, Sydney, NSW, Australia
³ School of Physics, The University of New South Wales, 2052, Sydney, NSW, Australia

^e g.pierobon@unsw.edu.au

Received: 23 June 2022
Accepted: 11 October 2022
Published online: 23 October 2022

Abstract

We study the phenomenology of the ‘companion-axion model’ consisting of two coupled QCD axions. The second axion is required to rescue the Peccei–Quinn solution to the strong-CP problem from the effects of colored gravitational instantons. We investigate here the combined phenomenology of axion–axion and axion–photon interactions, recasting present and future single-axion bounds onto the companion-axion parameter space. Most remarkably, we predict that future axion searches with haloscopes and helioscopes may well discover two QCD axions, perhaps even within the same experiment.

© The Author(s) 2022

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