High-quality axions in solutions to the μ problem

Solutions to the mu problem in supersymmetry based on the Kim-Nilles mechanism naturally feature a Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) axion with a decay constant of the order of the geometric mean of the Planck and TeV scales, consistent with astrophysical limits. We investigate minimal models of this type with two gauge-singlet fields that break a Peccei-Quinn symmetry and extensions with an extra vectorlike quark and lepton supermultiplets consistent with gauge coupling unification. We show that there are many anomaly-free discrete symmetries, depending on the vectorlike matter content, that protect the Peccei-Quinn symmetry to sufficiently high order to solve the strong CP problem. We study the axion couplings in this class of models. Models of this type that are automatically free of the domain wall problem require at least one pair of strongly interacting vectorlike multiplets with mass at the intermediate scale and predict axion couplings that are greatly enhanced compared to the minimal supersymmetric DFSZ models, putting them within reach of proposed axion searches.

Automated summary

Solutions to the mu problem in supersymmetry based on the Kim-Nilles mechanism naturally include a DFSZ axion with enhanced couplings, where anomaly-free discrete symmetries play a crucial role in protecting the Peccei-Quinn symmetry. These models require at least one pair of strongly interacting vectorlike multiplets at an intermediate scale to be free of the domain wall problem, making them promising for proposed axion searches.