Distinguishing Dirac and Majorana neutrinos by their gravi-majoron decays

Understand

Neutrinos may acquire small Dirac or Majorana masses by new low-energy physics in terms of the chiral gravitational anomaly, as proposed by Dvali and Funcke (2016).

• This model predicts fast neutrino decays, $\nu_i\to\nu_j+\phi$ and $\nu_i\to\bar{\nu}_j+\phi$, where the gravi-majorons $\phi$ are pseudoscalar Nambu-Goldstone bosons.
• The final-state neutrino and antineutrino distributions differ depending on the Dirac or Majorana mass of the initial state.
• This opens a channel for distinguishing these cases, for example in the spectrum of high-energy astrophysical neutrinos.