Revisiting pseudo-Dirac neutrinos

Abstract

We study the pseudo-Dirac mixing of left and right-handed neutrinos in the case where the Majorana masses M_L and M_R are small when compared with the Dirac mass, M_D. The light Majorana masses could be generated by a non-renormalizable operator reflecting effects of new physics at some high energy scale. In this context, we obtain a simple model independent closed bound for M_D. A phenomenologically consistent scenario is achieved with M_L,M_R ~ 10^{-7} eV and M_D ~ 10^{-5}-10^{-4} eV. This precludes the possibility of positive mass searches in the planned future experiments like GENIUS or in tritium decay experiments. If on the other hand, GENIUS does observe a positive signal for a Majorana mass \geq 10^{-3} eV, then with very little fine tuning of neutrino parameters, the scale of new physics could be in the TeV range, but pseudo-Dirac scenario in that case is excluded. We briefly discuss the constraints from cosmology when a fraction of the dark matter is composed of nearly degenerate neutrinos.

17 pages, no figures, references added, to be published in PLB

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• Pseudo-Dirac Neutrino Scenario: Cosmic Neutrinos at Neutrino Telescopes
• Neutrino masses in the economical 3-3-1 model
• The economical SU(3)_C X SU(3)_L X U(1)_X model
• Quasi Dirac neutrino oscillations
• Unraveling the Dirac Neutrino with Cosmological and Terrestrial Detectors
• Quasi-Dirac neutrino oscillations at DUNE and JUNO
• A Model for Pseudo-Dirac Neutrinos: Leptogenesis and Ultra-High Energy Neutrinos
• Late time supernova neutrino signal and proto-neutron star radius
• Effects of degenerate sterile neutrinos on the supernova neutrino flux
• Pseudo-Dirac Neutrinos and Relic Neutrino Matter Effect on the High-energy Neutrino Flavor Composition