Oscillation of Dirac and Majorana neutrinos from muon decay in the case   of a general interaction
  We analyse the possibility of distinguishing Dirac and Majorana neutrinos in future neutrino factory experiments in which neutrinos are produced in muon decay when, in addition to a vector type as in the SM, there are also scalar interactions. We check this possibility in an experiment with a near detector, where the observed neutrinos do not oscillate, and in a far detector, after the neutrino oscillations. Neglecting higher-order corrections, even neutrino observation in the near detector does not give a chance to differentiate their character. However, this possibility appears in the leading-order after the neutrino oscillations observed in far detector. 
Robert Szafron and Marek Zralek
hep-ph