Dirac-Majorana neutrinos distinction in four-body decays

Abstract

A novel method to differentiate the effects of Dirac and Majorana (D-M) neutrinos in four-body decays has been discussed in [C. S. Kim , Inferring the nature of active neutrinos: Dirac or Majorana?, .]. There, it is concluded that the back-to-back kinematic scenario seems to avoid the constraint imposed by the “practical Dirac-Majorana confusion theorem,” as one does not need to fully integrate over neutrino and antineutrino momenta. In this paper, we propose to analyze radiative leptonic lepton-decays (ℓ→ℓ′νν¯γ), as an independent alternative process to study the possible Majorana nature of neutrinos. Our approach demonstrates that, in the back-to-back kinematic configuration (for the ℓ′−γ and ν−ν¯ systems, respectively), the distinction between Dirac and Majorana cases disappears when the inaccessible neutrino angle is integrated out, which might appear unexpected considering the claims in [C. S. Kim , Inferring the nature of active neutrinos: Dirac or Majorana?, .]. Our results apply in absence of nonstandard interactions, which can enhance generally the sensitivity to the neutrino nature. Published by the American Physical Society 2024