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Probing Anomalous Top-Quark Couplings Induced by Dim.6 Operators at Photon Colliders

Possible anomalous top-quark couplings induced by SU(2) x U(1) gauge-invariant dimension-6 effective operators were studied in the process of t t-bar productions and decays at polarized gamma gamma colliders. Two CP-violating asymmetries, a linear-polarization asymmetry and a circular-polarization asymmetry, were computed including both non-standard [t t-bar gamma] and [gamma gamma H] couplings. An optimal-observable analysis for the process gamma gamma --> t t-bar --> l^{+-} ... was performed in order to estimate the precision for determination of all relevant non-standard couplings, including the anomalous tbW coupling.