Top Quark Polarization in e+e- Annihilation near Threshold

Polarization studies can play important role in the determination of the electroweak charges of the top quark. A particularly useful reaction is top quark pair production near threshold at future linear e⁺e^- colliders. Top quark polarization in e⁺e^- annihilation into t t¯ is calculated for linearly polarized beams. The Green function formalism is applied to this reaction near threshold. S-P-wave interference contributes to all components of the top quark polarization vector. Rescattering of the decay products is also considered. The mean values < nl> of the charged lepton four-momentum projections on appropriately chosen four-vectors n in semileptonic top decays are experimentally observable quantities sensitive to the top quark polarization. It is demonstrated that for a longitudinally polarized electron beam a highly polarized sample of top quarks can be produced.