Probing the Weak Boson Sector in γe → Ze

We study possible deviations from the standard model in the reaction γe → Ze at a 500 GeV e + e − collider. As a photon source we use a laser backscattered photon beam. We investigate the most general γZγ and γZZ vertices including operators up to energy-dimension-six which are Lorentz invariant. These vertices require four extra parameters; two are CP-conserving, h γ 1 and h Z 1 , and two are CP-violating, h γ 2 and h Z 2. We present analytical expressions of the helicity amplitudes for the process γe → Ze for arbitrary values of anomalous couplings. Assuming Standard Model values are actually measured we present the allowed region in the (h γ 1 , h Z 1) plane at the 90% confidence level. We then show how the angular correlation of the Z decay products can be used to extract detailed information on the anomalous (especially CP-violating) γZγ and γZZ couplings.