The $\eta -{\eta }^{\mathrm{\prime }}$ Mixing Angle Revisited

The value of the $\eta -{\eta }^{\mathrm{\prime }}$ mixing angle ${\theta }_P$ is phenomenologically deduced from a rather exhaustive and up-to-date analysis of data including strong decays of tensor and higher-spin mesons, electromagnetic decays of vector and pseudoscalar mesons, $J\mathrm{/}\psi$ decays into a vector and a pseudoscalar meson, and other transitions. A value of ${\theta }_P$ between $-{17}^{\circ }$ and $-{13}^{\circ }$ is consistent with all the present experimental evidence and the average ${\theta }_P=-{15.5}^{\circ }\pm {1.3}^{\circ }$ seems to be favoured.