A test of gauge nature of the W boson in the reaction e⁺e^- → Zγ

I propose a new method to measure the magnetic moment parameter κ of the charged intermediate weak boson. T-odd asymmetries in the angular distribution of the secondary lepton in the process e⁺e^- → Z_γ, Z → ℓℓ are very sensitive to κ. The asymmetric are calculated in the lowest order from the absorptive part of one-loop diagrams.