QCD Axion as a Bridge Between String Theory and Flavor Physics

TL;DR

This paper develops a string-inspired model linking flavor physics and string theory through flavored PQ axions, addressing fermion mass hierarchy and the strong CP problem with novel moduli stabilization.

Contribution

It introduces a model with two anomalous gauged U(1) symmetries that connect string theory to flavor physics and constrains the potential contributions, stabilizing moduli while preserving flavored PQ axions.

Findings

Two axions remain massless after stabilization.

The model constrains F- and D-term contributions to the potential.

Surviving axions serve as flavored PQ axions at low energies.

Abstract

We construct a string-inspired model, motivated by the flavored Peccei-Quinn (PQ) axions, as a useful bridge between flavor physics and string theory. The key feature is two anomalous gauged $U(1)$ symmetries, responsible for both the fermion mass hierarchy problem of the standard model and the strong CP problem, that combine string theory with flavor physics and severely constrain the form of the F- and D-term contributions to the potential. In the context of supersymmetric moduli stabilization we stabilize the size moduli with positive masses while leaving two axions massless and one axion massive. We demonstrate that, while the massive gauge bosons eat the two axionic degrees of freedom, two axionic directions survive to low energies as the flavored PQ axions.