The Window for Preferred Axion Models
INFN – Laboratori Nazionali di Frascati
I discuss phenomenological criteria for defining an “axion window”, namely a region of parameter space for the axion-photon coupling as a function of the axion mass, where realistic models live. Currently, the boundaries of this region depend on somewhat arbitrary criteria, and it would be desirable to specify them in terms of precise phenomenological requirements. Focusing on hadronic axion models, I classify the representations of the new heavy quarks by requiring that the are sufficiently short lived to avoid issues with long lived strongly interacting relics, the theory remains weakly coupled up to the Planck scale. Next, I discuss the general case of multiple , identifying the absolute upper and lower bound on the axion-photon coupling. I conclude with some comments on the window for DFSZ-type of axion models.