<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math> -boson decays into Majorana or Dirac heavy neutrinos

We computed the kinematics of $Z$-boson decay into a heavy--light neutrino pair when is produced at rest in ${e}^{+}{e}^{\ensuremath{-}}$ collisions, including subsequent heavy visible final state containing charged-lepton. concentrated on heavy-neutrino masses order dozens GeV and issue addressing nature neutrinos---Dirac fermions or Majorana fermions. find that while it not possible to tell light neutrinos an event-by-event basis, can nonetheless be inferred given large-enough sample pairs. identify two observables sensitive neutrinos. One forward-backward asymmetry daughter-charged-leptons. This exactly zero if are nonzero (and opposite) for positively- negatively-charged daughter-leptons Dirac The other observable polarization neutrino, imprinted laboratory-frame energy distribution antineutrinos collisions $Z$-pole strongly polarized most as $Z$-bosons.