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

Abstract

The value of the $\eta -{\eta }^{\prime }$ 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, $J/\psi$ 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.

Comments: 17 pages, LaTeX. 2 references added, some comments on Chiral Perturbation Theory