Anomaly Ratio Distributions of Hadronic Axion Models with Multiple Heavy Quarks

Understand

We consider hadronic axion models that extend the Standard Model by one complex scalar field and one or more new heavy quarks, i.e.

• $N_\mathcal{Q} \geq 1$.
• We review previously suggested selection criteria as well as categorize and catalog all possible models for $N_\mathcal{Q} \leq 9$.
• In particular, allowing for $N_\mathcal{Q} > 1$ can introduce models that spoil the axion solution of the strong CP problem.