A Tale of Two-U(1) Axion Models

Abstract

The $U(1)$ global symmetry to solve the strong $CP$ problem could be the remnant of multi-$U(1)$ symmetries from QCD and hidden strong dynamics. Both Peccei-Quinn $U(1)$ and dynamical $U(1)$ are described uniformly, based on which we classify various mixed two-$U(1)$ models to solve both strong $CP$ and quality problems. We propose a moose diagram method with different fermion assignments to directly read relations between $CP$ phases, which illustrate how strong $CP$ problem is solved in terms of cancellation between $CP$ phases. In two axion models, we find the lightest axion is still same as QCD axion at infrared region, while one axion model with $Z_2$ symmetry enhances the axion mass spectrum. Our discussions can be extended to multi-axion cases.

25 pages, 3 figures

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• Echoes of a Hidden Valley at Hadron Colliders
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• Natural inflation with multiple sub-Planckian axions
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Cited by in corpus (2)

• Phenomenology of the companion-axion model: photon couplings
• Cosmology of the companion-axion model: dark matter, gravitational waves, and primordial black holes