Simple decay-lepton asymmetries in polarized e+e- -> t tbar and CP-violating dipole couplings of the top quark

We study two simple $CP$-violating asymmetries of leptons coming from the decay of $t$ and $\o t$ in $e^+e^- \ra \tt$, which do not need the full reconstruction of the $t$ or $\o t$ for their measurement. They can arise when the top quark possesses nonzero electric and weak dipole form factors in the couplings to the photon and $Z$, respectively. Together, these two asymmetries can help to determine the electric and weak dipole form factors independently. If longitudinal beam polarization is available, independent determination of form factors can be done by measuring only one of the asymmetries. We obtain estimates of 90\% confidence limits that can be put on these form factors at a future linear $\ee$ collider operating at $\sqrt{s}=500$ GeV.