A QCD R-Axion

TL;DR

This paper explores the possibility that an anomalous U(1)${}_R$ symmetry in supersymmetric models can serve as the Peccei-Quinn symmetry, with the R-axion acting as the QCD axion, potentially solving the strong CP problem.

Contribution

It proposes a novel identification of the U(1)${}_R$ symmetry as the PQ symmetry and discusses how it can be gauged to address the axion quality problem.

Findings

U(1)${}_R$ can be broken at an intermediate scale to produce the QCD axion.

Gauging the R-symmetry via the Green-Schwartz mechanism can evade the axion quality problem.

Phenomenologically viable models with an R-axion as the QCD axion are identified.

Abstract

R-parity can be extended to a continuous global U(1)${}_R$ symmetry. We investigate whether an anomalous U(1)${}_R$ can be identified as the PQ symmetry suitable for solving the strong CP problem within supersymmetric extensions of the Standard Model. In this case, U(1)${}_R$ is broken at some intermediate scale and the QCD axion is the R-axion. Moreover, the R-symmetry can be naturally gauged via the Green-Schwartz mechanism within completions to supergravity, thus evading the axion quality problem. Obstacles to realizing this scenario are highlighted and phenomenologically viable approaches are identified.