Heavy meson chiral perturbation theory constraints on a charm-coupled GeV-scale QCD axion

Bo-Qiang Lu

The QCD axion with charm-only Peccei-Quinn coupling evades the isospin-violation problem of light-quark models in $\chi$PT. Since $m_c>{\Lambda }_{\mathrm{QCD}}$, we employ heavy meson chiral pertu…