Probing Majorana neutrinos in rare π + → e + e + μ − ν decays

Abstract

We study the rare decays of charged π mesons, π + → e + e + μ − $ \overline v $ μ and π + → e + μ − e + ν e induced by a sterile neutrino N with a mass in the range m μ < m N < m π . The first process violates Lepton Number by two units and so occurs only if N is Majorana, while the second process conserves Lepton Number and occurs irrespective of the Majorana or Dirac character of N . We study a way to distinguish the Majorana vs. Dirac character of N in these processes using the muon spectrum. We also find that the branching ratios could be at the reach of high luminosity experiments like Project X at FNAL or any proposed neutrino (or muon) factories worldwide.