The $η- η'$ Mixing Angle Revisited

Abstract

The value of the $η- η'$ mixing angle $θ_P$ 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, $J/ψ$ decays into a vector and a pseudoscalar meson, and other transitions. A value of $θ_P$ between $-17^\circ$ and $-13^\circ$ is consistent with all the present experimental evidence and the average $θ_P=-15.5^\circ\pm 1.3^\circ$ seems to be favoured.