Quasi Dirac neutrino oscillations

Abstract

Dirac neutrino masses require two distinct neutral Weyl spinors per generation, with a special arrangement of masses and interactions with charged leptons. Once this arrangement is perturbed, lepton number is no longer conserved and neutrinos become Majorana particles. If these lepton number violating perturbations are small compared to the Dirac mass terms, neutrinos are quasi-Dirac particles. Alternatively, this scenario can be characterized by the existence of pairs of neutrinos with almost degenerate masses, and a lepton mixing matrix which has 12 angles and 12 phases. In this work we discuss the phenomenology of quasi-Dirac neutrino oscillations and derive limits on the relevant parameter space from various experiments. In one parameter perturbations of the Dirac limit, very stringent bounds can be derived on the mass splittings between the almost degenerate pairs of neutrinos. However, we also demonstrate that with suitable changes to the lepton mixing matrix, limits on such mass splittings are much weaker, or even completely absent. Finally, we consider the possibility that the mass splittings are too small to be measured and discuss bounds on the new, non-standard lepton mixing angles from current experiments for this case.

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• Probing Neutrino Dirac Mass in Left-Right Symmetric Models at the LHC and Next Generation Colliders
• Probing nonstandard lepton number violating interactions in neutrino oscillations
• Probing New Physics with Long-Range Neutrino Interactions: An Effective Field Theory Approach
• Revisiting pseudo-Dirac neutrino scenario after recent solar neutrino data
• Constraining super-light sterile neutrinos at Borexino and KamLAND
• Pseudo-Dirac Neutrinos and Relic Neutrino Matter Effect on the High-energy Neutrino Flavor Composition
• How Broad is a Neutrino?
• Testing quasi-Dirac leptogenesis through neutrino oscillations
• On the collider-testability of the type-I seesaw model with 3 right-handed neutrinos
• Constraining the pseudo-Dirac nature of neutrinos using astrophysical neutrino flavor data
• Analytic Neutrino Oscillation Probabilities
• Consequences of Neutrinoless Double Decays Dominated by Short Range Interactions
• Boomerang mechanism explaining the excess radio background
• Theory and phenomenology of Dirac neutrinos