Energy Spectrum of Secondary Leptons in e^+ e^- to tbar{t} - Non-standard Interactions and CP Violation -

The process of top-quark pair production at future high-energy $e^+ e^-$ linear colliders has been investigated as a possible test of physics beyond the Standard Model. Non-standard interactions have been assumed both for the production and for the subsequent decay of the top quarks. The energy spectrum of the single lepton $l^\pm$ and the energy correlation of $l^+$ and $l^-$ emerging from the process $e^+e^-\to t\bar{t}\to l^\pm X/l^+l^-X$ are calculated. The energy- spectrum asymmetry of $l^+$ and $l^-$ is considered as a measure of CP violation. An optimal method to determine whether CP violation occurs in the production or in the decay processes is proposed.