Probing the Weak Boson Sector in $\gamma e\to Ze$

Abstract

We study possible deviations from the standard model in the reaction $\gamma e\to Ze$ at a 500 GeV $e^{+}{e}^{-}$ collider. As a photon source we use a laser backscattered photon beam. We investigate the most general $\gamma Z\gamma$ and $\gamma ZZ$ vertices including operators up to energy-dimension-six which are Lorentz invariant. These vertices require four extra parameters; two are CP-conserving, $h_1^{\gamma }$ and $h_1^Z$, and two are CP-violating, $h_2^{\gamma }$ and $h_2^Z$. We present analytical expressions of the helicity amplitudes for the process $\gamma e\to Ze$ for arbitrary values of anomalous couplings. Assuming Standard Model values are actually measured we present the allowed region in the ($h_1^{\gamma },h_1^Z$) 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) $\gamma Z\gamma$ and $\gamma ZZ$ couplings.

Comments: Latex, 25 pages, 12 figures (not included). One compressed postscript file including all the figures available at ftp://ftp.kek.jp/kek/preprints/TH/TH-420/kekth420.ps.gz