Lepton distribution in top decay: A probe of new physics and top-polarization

We investigate the possibilities of studying new physics in various processes of t-quark production using kinematical distributions of the secondary lepton coming from decay of t quarks. We show that the angular distributions of the secondary lepton are insensitive to the anomalous tbW vertex and hence are pure probes of new physics in a generic process of t-quark production. The effects of t polarization on the distributions of the decay lepton are demonstrated for top-pair production process at a γγ-collider mediated by a heavy Higgs boson.