Naturally Light Dirac and Pseudo-Dirac Neutrinos from Left-Right Symmetry

Abstract

We develop a class of left-right symmetric theories based on the gauge group $SU(3{)}_c\times SU(2{)}_L\times SU(2{)}_R\times U(1)$ with a generalized seesaw mechanism for generating the charged fermion masses. Neutrinos are naturally Dirac particles in this setup with their small masses arising from two-loop quantum corrections. We evaluate these two-loop diagrams exactly and analyze the flavor structure of the lepton sector. We find excellent fits to neutrino oscillation data, independent of the right-handed gauge symmetry breaking scale. We also explore the possibility that neutrinos are pseudo-Dirac particles in this framework, with the tiny mass splittings between active and sterile neutrinos arising from Planck-induced corrections and find possible realizations. These models can be tested in the near future with precision cosmological measurements of $\Delta N_{\mathrm{eff}}$ in CMB which is predicted to be $\simeq 0.14$. This class of models allows for a solution to the strong CP problem via parity symmetry without the need for an axion.

18 pages and references, 4 figures

References in corpus (9)

• CMB-S4 Science Case, Reference Design, and Project Plan
• Pathways to Naturally Small Dirac Neutrino Masses
• Pseudo-Dirac Neutrinos in the New Standard Model
• Simplest Radiative Dirac Neutrino Mass Models
• Evaluating The Two Loop Diagram Responsible For Neutrino Mass In Babu's Model
• SN1987A still shining: A Quest for Pseudo-Dirac Neutrinos
• Observing Left-Right Symmetry in the Cosmic Microwave Background
• Vector-Like Quarks and Leptons, SU(5) $\otimes$ SU(5) Grand Unification, and Proton Decay
• Left-Right Symmetric Model without Higgs Triplets

Cited by in corpus (9)

• Novel loop-diagrammatic approach to QCD $\theta$ parameter and application to the left-right model
• Probing Pseudo-Dirac Neutrinos with Astrophysical Sources at IceCube
• Revisiting the Dirac Nature of Neutrinos in the Light of $\Delta (27)$ and Cyclic Symmetries
• Relic neutrino decay solution to the excess radio background
• Pseudo-Dirac Neutrinos and Relic Neutrino Matter Effect on the High-energy Neutrino Flavor Composition
• P and CP solution of the strong CP puzzle
• Radiative Origin of Fermion Mass Hierarchy in Left-Right Symmetric Theory
• Cosmogenic neutrinos as probes of new physics
• Boomerang mechanism explaining the excess radio background