Can we distinguish Dirac and Majorana neutrinos produced in muon decay?

Abstract

Neutrinos produced in the muon decay scatter on electrons in the near (without oscillation) and in the far detector (after oscillation) and the numer of produced muons is observed. In the frame of the Standard Model the cross-section for muon production does not depend on the neutrino nature. The situation is different, if beyond the SM neutrino interactions are present. We use the Fermi contact model, where we allow only one additional coupling, the charged scalar right-handed coupling which appear in variety of models. No bounds on the new scalar coupling for Majorana neutrino are found. The cross-sections for muon production is different for Dirac and Majorana neutrinos giving in principle possibility to distinguish their nature. The differences between the Dirac and Majorana cross-sections appear in the near and in the far detector. The cross-section for both types of neutrinos is different even if neutrinos do not oscillate, but the difference is larger after oscillation, even in the vacuum.