A class of invisible axion models with FCNCs at tree level

Understand

We build a class of invisible axion models with tree-level Flavor Changing Neutral Currents completely controlled by the fermion mixing matrices.

• The scalar sector of these models contains three-Higgs doublets and a complex scalar gauge singlet, with the same fermionic content than the Standard Model.
• A horizontal Peccei-Quinn symmetry provides a solution to the strong CP problem and predicts the existence of a very light and weakly coupled pseudo-Goldstone boson, the invisible axion or familon.
• A phenomenological analysis is performed taking into account familon searches in rare kaon and muon decays, astrophysical considerations and axion searches via axion-photon conversion.