  We study the possibility of future $e^{+}e^{-}$ colliders to disentangle
different new physics contributions to the production of heavy sterile Majorana
neutrinos in the lepton number violating channel $e^{+}e^{-}\rightarrow l^{+}
l^{+}+ 4 jets$, with $l=e, \mu, \tau$. This is done investigating the final
anti-tau polarization trails and initial beam polarization dependence of the
signal on effective operators with distinct Dirac-Lorentz structure
contributing to the Majorana neutrino production and decay, which parameterize
new physics from a higher energy scale. We find both analyses could well
disentangle possible vectorial and scalar operators contributions.
