An A4-symmetric double seesaw for neutrino masses and mixing in light of JUNO results
5 affiliations
- 1SOA University
- 2Gauhati University
- 3Utkal University
- 4Indian Institute of Technology Bhilai
- 5Institute of Physics
Abstract
A bstract : We investigate the double seesaw mechanism for generating light neutrino masses within a Standard Model extension containing three right-handed neutrinos and three gauge-singlet sterile fermions. The flavour structure is governed by an A ₄ discrete symmetry, which leads to predictive textures for the Dirac neutrino mass matrix M D , the right-handed-sterile neutrino mixing matrix M RS , and the sterile-sector Majorana mass matrix M S . With suitable A ₄ charge assignments and simple flavon vacuum alignments, the model naturally realizes a leading-order tribimaximal (TBM) mixing pattern corrected by a single complex rotation in the (1 , 3) sector, resulting in the exact TM ₂ mixing structure. This framework successfully reproduces the observed reactor mixing angle while providing predictive relations among the neutrino masses, mixing parameters, and CP-violating phases. The recent high-precision JUNO determination of the solar mixing angle, however, places the exact TM ₂ prediction, sin ² θ ₁₂ ≃ 0 . 341, in significant tension with the experimental data. Motivated by this discrepancy, we extend the exact TM ₂ framework by introducing a small perturbation in the sterile-sector Majorana mass matrix, leading to a generalized TM ₂ mixing structure. The additional degree of freedom relaxes the rigid TM ₂ sum rule and allows the solar mixing angle to vary over the experimentally preferred region while preserving the successful predictions for the reactor and atmospheric mixing angles. A comprehensive numerical analysis is performed using the latest JUNO and NuFIT 6.1 neutrino oscillation data. The generalized TM ₂ framework successfully reproduces the observed neutrino mass spectrum and mixing parameters, predicts characteristic correlations among CP-violating phases and oscillation observables, and yields phenomenologically viable regions for neutrinoless double beta decay. The interplay between the double seesaw mechanism, A ₄ flavour symmetry, and the generalized TM ₂ structure therefore provides a predictive and experimentally testable framework for understanding neutrino masses and flavour mixing.
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BibTeX
@article{nanda2026a4symmetric,
title = {{An A4-symmetric double seesaw for neutrino masses and mixing in light of JUNO results}},
author = {Swaraj Kumar Nanda and Maibam Ricky Devi and Chandini Dash and R. N. Panda and Sudhanwa Patra},
journal = {Journal of High Energy Physics},
year = {2026},
month = nov,
doi = {10.1007/jhep11(2026)045},
url = {https://link.springer.com/article/10.1007/JHEP11(2026)045},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - An A4-symmetric double seesaw for neutrino masses and mixing in light of JUNO results
AU - Swaraj Kumar Nanda
AU - Maibam Ricky Devi
AU - Chandini Dash
AU - R. N. Panda
AU - Sudhanwa Patra
PY - 2026
DA - 2026/11/05
JO - Journal of High Energy Physics
DO - 10.1007/jhep11(2026)045
UR - https://link.springer.com/article/10.1007/JHEP11(2026)045
AB - A bstract : We investigate the double seesaw mechanism for generating light neutrino masses within a Standard Model extension containing three right-handed neutrinos and three gauge-singlet sterile fermions. The flavour structure is governed by an A ₄ discrete symmetry, which leads to predictive textures for the Dirac neutrino mass matrix M D , the right-handed-sterile neutrino mixing matrix M RS , and the sterile-sector Majorana mass matrix M S . With suitable A ₄ charge assignments and simple flavon vacuum alignments, the model naturally realizes a leading-order tribimaximal (TBM) mixing pattern corrected by a single complex rotation in the (1 , 3) sector, resulting in the exact TM ₂ mixing structure. This framework successfully reproduces the observed reactor mixing angle while providing predictive relations among the neutrino masses, mixing parameters, and CP-violating phases. The recent high-precision JUNO determination of the solar mixing angle, however, places the exact TM ₂ prediction, sin ² θ ₁₂ ≃ 0 . 341, in significant tension with the experimental data. Motivated by this discrepancy, we extend the exact TM ₂ framework by introducing a small perturbation in the sterile-sector Majorana mass matrix, leading to a generalized TM ₂ mixing structure. The additional degree of freedom relaxes the rigid TM ₂ sum rule and allows the solar mixing angle to vary over the experimentally preferred region while preserving the successful predictions for the reactor and atmospheric mixing angles. A comprehensive numerical analysis is performed using the latest JUNO and NuFIT 6.1 neutrino oscillation data. The generalized TM ₂ framework successfully reproduces the observed neutrino mass spectrum and mixing parameters, predicts characteristic correlations among CP-violating phases and oscillation observables, and yields phenomenologically viable regions for neutrinoless double beta decay. The interplay between the double seesaw mechanism, A ₄ flavour symmetry, and the generalized TM ₂ structure therefore provides a predictive and experimentally testable framework for understanding neutrino masses and flavour mixing.
SN - 1029-8479
ER -