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 dimension6 effective operators were studied in the process of t (t) over bar productions and decays at polarized gammagamma colliders. Two CP-violating asymmetries, a linear-polarization asymmetry and a circular-polarization asymmetry, were computed including both non-standard t(t) over bar gamma and gammagammaH couplings. An optimal-observable analysis for the process gammagamma --> t (t) over bar --> l(+/-) ... was performed in order to estimate the precision for determination of all relevant non-standard couplings, including the anomalous tbW coupling. (C) 2004 Elsevier B.V. All rights reserved.