Flavour from the Axion: Predictive DFSZ Textures and Their Phenomenology
ABSTRACT
The Peccei–Quinn symmetry that solves the strong CP problem need not be flavour-blind. If it acts horizontally on the Standard Model quarks, a single anomalous $U(1)_{PQ}$ can simultaneously address the strong CP problem, supply a QCD axion dark matter candidate, and shape the fermion mass matrices. I will present the Minimal F-DFSZ framework: a class of flavoured DFSZ models in which the PQ symmetry is fully horizontal and the domain wall number is unity, allowing for a cosmologically viable post-inflationary axion. The horizontal charges enforce predictive texture-zero Yukawa matrices, so that the axion- and Higgs-mediated flavour-changing couplings are fixed in terms of Standard Model observables. I will discuss the phenomenology that follows — spanning axion, Higgs, and precision-flavour observables — and show how the predictivity of the framework translates into concrete constraints on the scale of new physics.
