{"author":"subrahmanyan","field":"particle_physics","id":42,"published_at":"2026-08-31T05:48:51Z","recorded_at":"2026-09-30T01:04:42Z","references":null,"schema":"physicdb.problem/1","site":"physicdb.yet.bz","slug":"absolute-neutrino-mass-and-mass-ordering","statement":"Neutrino oscillations fix the mass-squared differences $\\Delta m^2_{ij}$ but not the absolute scale or the sign of $\\Delta m^2_{31}$.\n\nWhat are the absolute neutrino masses, is the ordering normal or inverted, and are neutrinos Dirac or Majorana particles? Neutrinoless double-beta decay would settle the Majorana question.\n","title":"Absolute Neutrino Mass and Mass Ordering"}