Neutrino Mass in Left-Right Symmetry: From Majorana Signals to Dirac Predictions
Abstract
We review neutrino mass as a probe of restored parity in left-right symmetric theories, emphasizing the distinct Majorana and Dirac realizations. In the Majorana theory, lepton-number violation connects the seesaw mechanism to neutrinoless double beta decay, heavy-neutrino production and the Keung-Senjanovic process. The Dirac alternative removes these characteristic signals while retaining a relation between left- and right-handed flavor. The right-handed leptonic mixing matrix can then be reconstructed from low-energy data and the spontaneous parity-breaking parameter. Requiring the two lepton Yukawa matrices to admit a common real parity basis turns this reconstruction into a compatibility condition that determines the allowed Dirac phase on each branch. For three generations, this requirement reduces to a single rephasing-invariant CP-odd obstruction, which also governs the right-left modulus mismatch and the relative CP orientation. The small Dirac masses also restrict the parity deformation and its induced strong-CP phase. For compressed mixed-sign neutrino spectra, a tiny parity deformation can nevertheless generate large leptonic CP violation, despite stringent strong-CP constraints. The resulting branch-dependent correlations connect leptonic CP, the absolute neutrino mass and strong CP. We place this construction alongside radiative and unified approaches to predicting leptonic CP violation.
Related
- When can decoherence reveal a Majorana phase? A phase-covariance no-go theorem for two-flavor neutrino oscillations
- Majorana Neutrino Physics and Matter-Antimatter Asymmetry in Type IIA String Theory
- Muon-to-positron conversion from light Majorana neutrino exchange: nuclear responses and pion-pole-improved multipoles
- Purely flavon driven leptogenesis for exactly degenerate Dirac or Majorana neutrino mass matrix in the type-I seesaw model
- Right-handed neutrino dark matter consistent with the generation of baryon number asymmetry
BibTeX
@misc{tello2026neutrino,
title = {{Neutrino Mass in Left-Right Symmetry: From Majorana Signals to Dirac Predictions}},
author = {Vladimir Tello},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.31658},
eprint = {2610.31658},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.31658},
}
RIS
TY - UNPB
TI - Neutrino Mass in Left-Right Symmetry: From Majorana Signals to Dirac Predictions
AU - Vladimir Tello
PY - 2026
DA - 2026/10/22
PB - arXiv
DO - 10.48550/arxiv.2610.31658
UR - https://arxiv.org/abs/2610.31658
AB - We review neutrino mass as a probe of restored parity in left-right symmetric theories, emphasizing the distinct Majorana and Dirac realizations. In the Majorana theory, lepton-number violation connects the seesaw mechanism to neutrinoless double beta decay, heavy-neutrino production and the Keung-Senjanovic process. The Dirac alternative removes these characteristic signals while retaining a relation between left- and right-handed flavor. The right-handed leptonic mixing matrix can then be reconstructed from low-energy data and the spontaneous parity-breaking parameter. Requiring the two lepton Yukawa matrices to admit a common real parity basis turns this reconstruction into a compatibility condition that determines the allowed Dirac phase on each branch. For three generations, this requirement reduces to a single rephasing-invariant CP-odd obstruction, which also governs the right-left modulus mismatch and the relative CP orientation. The small Dirac masses also restrict the parity deformation and its induced strong-CP phase. For compressed mixed-sign neutrino spectra, a tiny parity deformation can nevertheless generate large leptonic CP violation, despite stringent strong-CP constraints. The resulting branch-dependent correlations connect leptonic CP, the absolute neutrino mass and strong CP. We place this construction alongside radiative and unified approaches to predicting leptonic CP violation.
ER -