Comment on "Improved measurement of $\eta/\eta'$ mixing in $B_{(s)}^0\to J/\psi \eta^{(\prime)}$ decays"

Abstract

Instead of the glueball-$\eta'$ mixing ansatz, the latest measured ratios of the branching fractions of $B_{(s)}^0\to J/\psi \eta^{(\prime)}$ decays by LHCb can be understood by including the contribution from the light quark annihilation effect enhanced by the QCD $\mathrm{U}_A(1)$ anomaly for light pseudoscalar mesons.