An invisible axion model with controlled FCNCs at tree level

TL;DR

This paper develops a new class of invisible axion models with controlled flavor-changing neutral currents at tree level, addressing the strong CP problem, dark matter, and neutrino masses, while avoiding domain wall issues.

Contribution

It introduces explicit models where flavor-changing neutral currents are governed by fermion mixing, integrating solutions for the strong CP problem, dark matter, and neutrino mass origin.

Findings

Models predict axion-photon coupling within experimental limits

Proposes mechanisms to avoid the domain wall problem

Discusses astrophysical and rare decay constraints

Abstract

We derive the necessary conditions to build a class of invisible axion models with Flavor Changing Neutral Currents at tree-level controlled by the fermion mixing matrices and present an explicit model implementation. A horizontal Peccei-Quinn symmetry provides a solution to the strong CP problem via the Peccei-Quinn mechanism and predicts a cold dark mater candidate, the invisible axion or familon. The smallness of active neutrino masses can be explained via a type I seesaw mechanism, providing a dynamical origin for the heavy seesaw scale. The possibility to avoid the domain wall problem stands as one of the most interesting features of the type of models considered. Experimental limits relying on the axion-photon coupling, astrophysical considerations and familon searches in rare kaon and muon decays are discussed.