$ηγZ$ anomaly from the $η-->γμ+μ-$ decay

Abstract We show that the ηγZ anomaly can be measured by analysing parity-violating effects in the η → γμ + μ − decay. In this sense, we find that the longitudinal polarization of the outgoing μ + is an appropriate observable to be considered in future high-statistics η factories. The effect is expected to lie in the range 10 −5 –10 −6 in the Standard Model.