CP-violating lepton-energy correlation in ee → tt

In order to observe a signal of possible CP violation in top-quark couplings, we have studied the energy correlation of the final leptons in e+e− → tt → l+l−Xl±X at future linear colliders. Applying the recently-proposed optimal method, we have compared the statistical significances of CP-violation-parameter determination using double- and single-lepton distributions. We have found that the single-lepton-distribution analysis is more advantageous.