Pheno-Coffee Talk

Speaker: P. S. Bhupal Dev (Washington University in St. Louis, U.S.A.)

Title: Neutrinos: Dirac or Majorana?

Abstract: Whether neutrinos are Dirac or Majorana particles is an open question in fundamental physics. Theoretically, it is also possible that neutrinos are pseudo-Dirac, which are fundamentally Majorana fermions, but essentially act like Dirac fermions in most experimental settings, due to extremely small active-sterile mass splitting. Such small values of mass splitting can be accessed via active-sterile oscillations over astrophysical baselines. We use the recent multi-messenger observations of high-energy neutrino sources to probe hitherto unexplored values of active-sterile mass splitting, which improve the reach of terrestrial experiments by more than a billion.