Dynamics of Superconformal Axion: Quality and Scalegenesis

TL;DR

This paper proposes a dynamical mechanism within supersymmetric QCD to naturally generate a global $U(1)_{PQ}$ symmetry and its breaking at an intermediate scale, addressing the strong CP problem with suppressed explicit breaking.

Contribution

It introduces a novel supersymmetric QCD-based dynamics near the conformal window that explains the emergence and breaking of the $U(1)_{PQ}$ symmetry at a hierarchically small scale.

Findings

Suppression of explicit $U(1)_{PQ}$-violating operators due to large anomalous dimensions.

Hierarchical $U(1)_{PQ}$ breaking scale generated by non-perturbative effects.

Stable saxion direction with cosmologically safe properties.

Abstract

We explore a dynamical mechanism to realize the emergence of a global $U(1)_{\rm PQ}$ symmetry and its spontaneous breaking at an intermediate scale for an axion solution to the strong CP problem. Such a dynamics is provided by a new supersymmetric QCD near the middle of conformal window that couples to fields spontaneously breaking the $U(1)_{\rm PQ}$ symmetry. A large anomalous dimension of the $U(1)_{\rm PQ}$ breaking fields leads to the suppression of explicit $U(1)_{\rm PQ}$-violating higher dimensional operators. The $U(1)_{\rm PQ}$ breaking vacuum is generated at a scale hierarchically smaller than the Planck scale by a non-perturbative effect. The $U(1)_{\rm PQ}$ breaking drives the conformal breaking, and all the new quarks become massive. The axion potential is generated by the ordinary color $SU(3)_C$ effect as the $U(1)_{\rm PQ}$ symmetry is only anomalous under the $SU(3)_C$. The saxion direction is stabilized by supersymmetry breaking and cosmologically harmless.