Model of visible QCD axion

Abstract

We pursue a class of visible axion models where the axion mass is enhanced by strong dynamics in a mirrored copy of the Standard Model in the line of the idea put forward by Rubakov. In particular, we examine the consistency of the models with laboratory, astrophysical, and cosmological constraints. As a result, viable parameter regions are found, where the mass of the axion is of $O(100)\text{ }\text{ }\mathrm{MeV}$ or above while the Peccei-Quinn breaking scale is at around ${10}^{3--5}\text{ }\text{ }\mathrm{GeV}$.