Axion quality problem: keep calm and baryon

A bstract Axion models generically suffer from a severe quality problem when coupled to gravity. In this article we provide a very simple model with a high quality axion. The axion is a pseudo-Nambu-Goldstone boson of the baryon number symmetry, U(1) B , of a new composite sector that breaks U(1) B spontaneously when it confines. A controlled example is a supersymmetric QCD (SQCD) with N c = N f . The axion shift symmetry is automatically protected due to the high dimension of the gauge-invariant baryon operator, with the Peccei-Quinn breaking operators arising at dimension N c + 2. The standard model gauge group is embedded as a subgroup of the flavor symmetry group of SQCD that has an anomaly with U(1) B , generating the standard coupling with gluons.