On Non-Unitary Lepton Mixing and Neutrino Mass Observables

Abstract

There are three observables related to neutrino mass, namely the kinematic mass in direct searches, the effective mass in neutrino-less double beta decay, and the sum of neutrino masses in cosmology. In the limit of exactly degenerate neutrinos there are very simple relations between those observables, and we calculate corrections due to non-zero mass splitting. We discuss how the possible non-unitarity of the lepton mixing matrix may modify these relations and find in particular that corrections due to non-unitarity can exceed the corrections due to mass splitting. We furthermore investigate constraints from neutrino-less double beta decay on mass and mixing parameters of heavy neutrinos in the type I see-saw mechanism. There are constraints from assuming that heavy neutrinos are exchanged, and constraints from assuming light neutrino exchange, which arise from an exact see-saw relation. The latter has its origin in the unitarity violation arising in see-saw scenarios. We illustrate that the limits from the latter approach are much stronger. The drastic impact on inverse neutrino-less double beta decay (e e -> W W) is studied. We furthermore discuss neutrino mixing in case there is one or more light sterile neutrino. Neutrino oscillation probabilities for long baseline neutrino oscillation experiments are considered, and the analogy to general non-unitarity phenomenology, such as zero-distance effects, is pointed out.

16 pages, 2 figures. To appear in PLB

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Cited by in corpus (15)

• Flavor structures of charged fermions and massive neutrinos
• Sterile neutrinos in lepton number and lepton flavor violating decays
• Naturalness, Vacuum Stability and Leptogenesis in the Minimal Seesaw Model
• The minimal scenario of leptogenesis
• Vanishing effective mass of the neutrinoless double beta decay including light sterile neutrinos
• The minimal seesaw and leptogenesis models
• Inverse Neutrino-less Double Beta Decay Revisited: Neutrinos, Higgs Triplets and a Muon Collider
• Non-standard interaction in neutrino oscillations and recent Daya Bay, T2K experiments
• Intrinsic Deviation from the Tri-bimaximal Neutrino Mixing in a Class of A_4 Flavor Models
• TeV-scale seesaw mechanism catalyzed by the electron mass
• Non-unitarity of the leptonic mixing matrix in the TeV-scale type-I seesaw model
• Precision measurements and tau neutrino physics in a future accelerator neutrino experiment
• CP violation in bipair neutrino mixing
• Renormalization Group Evolution of the Non-Unitary operator
• Light sterile neutrino and leptogenesis