Axion Quality from Superconformal Dynamics

TL;DR

This paper explores how superconformal dynamics can naturally generate a global $U(1)_{PQ}$ symmetry to address the strong CP problem via the axion, with suppressed symmetry-violating operators and specific coupling structures.

Contribution

It proposes a novel mechanism where superconformal fixed points induce a large anomalous dimension, suppressing $U(1)_{PQ}$-violating operators and realizing the axion solution within a supersymmetric framework.

Findings

Superconformal dynamics lead to large anomalous dimensions of $U(1)_{PQ}$ breaking fields.

Suppression of higher-dimensional $U(1)_{PQ}$-violating operators.

A model with meson superfields in supersymmetric QCD realizing the $U(1)_{PQ}$ breaking.

Abstract

We discuss a possibility that a superconformal dynamics induces the emergence of a global $U(1)_{\rm PQ}$ symmetry to solve the strong CP problem through the axion. Fields spontaneously breaking the $U(1)_{\rm PQ}$ symmetry couple to new quarks charged under the ordinary color $SU(3)_C$ and a new $SU(N)$ gauge group. The theory flows into an IR fixed point where the $U(1)_{\rm PQ}$ breaking fields hold a large anomalous dimension leading to the suppression of $U(1)_{\rm PQ}$-violating higher dimensional operators. The spontaneous breaking of the $U(1)_{\rm PQ}$ makes the new quarks massive. The $U(1)_{\rm PQ}$ symmetry is anomalous under the $SU(3)_C$ but not under the $SU(N)$ so that the axion couples to only the color $SU(3)_C$ and the usual axion potential is generated. We also comment on a model that the $U(1)_{\rm PQ}$ breaking fields are realized as meson superfields in a new supersymmetric QCD.