IS THERE A CHANCE TO FIND HEAVY NEUTRINOS IN FUTURE LEPTON COLLIDERS

We examine two processes, the neutrino production process e(+)e(-) --> N nu and the inverse neutrinoless double-beta decay e(-)e(-) --> W-W- as possible places for discovering heavy neutrinos in future lepton l inear colliders. The heavy neutrino parameters are bound from existing experimental data. We use only one important theoretical input, the l ack of a Higgs triplet. As a consequence the neutrinos must have diffe rent CP parities, In such models the existing experimental bounds for mixing parameters still give a chance that heavy neutrinos can be obse rved in future e(+)e(-) and e(-)e(-) colliders.