$ηγZ$ 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.