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) 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). Thesmall 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 the 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.
Highlights
Introduction.—The strong CP problem is the puzzle of why the strong interactions are CP symmetric, even though the standard model (SM) as a whole is not
We consider a mirror sector in the UV related to the SM by a Z2 symmetry, generalizing on Refs. [9,10,11,12,13], coupled to the same axion, such that its contribution to the axion potential is much larger than QCD’s but aligned with it in having its minimum at θ 1⁄4 0
This results in an axion mechanism which is vastly more robust against other uncorrelated UVeffects
Summary
Introduction.—The strong CP problem is the puzzle of why the strong interactions are CP symmetric, even though the standard model (SM) as a whole is not. In the area labeled “Higgs VEV Quality Problem,” hH0i ∼ μ0 > 1014 GeV and Planck suppressed operators spoil the axion mechanism, as explained around Eq (6).
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