Distinguishing between Dirac and Majorana neutrinos in the presence of general interactions

We revisit the possibility of distinguishing between Dirac and Majorana neutrinos via neutrino-electron elastic scattering in the presence of all possible Lorentz-invariant interactions. Defining proper observables, certain regions of the parameter space can only be reached for Dirac neutrinos, but never for Majorana neutrinos, thus providing an al-ternative method to differentiate these two possibilities. We first derive analytically and numerically the most general conditions that would allow to distinguish Dirac from Ma-jorana neutrinos, both in the relativistic and non-relativistic cases. Then, we apply these conditions to data on ν μ -e and ν̄ₑ-e scatterings, from the CHARM-II and TEXONO experi-ments, and find that they are consistent with both types of neutrinos. Finally, we comment on future prospects of this kind of tests.