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arXiv · 2602.11277

Fate of $θ_{12}$ under $μ-τ$ Reflection Symmetry in Light of the First JUNO Results

Ranjeet Kumar
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Abstract

The recent Jiangmen Underground Neutrino Observatory (JUNO) measurements of $θ_{12}$ and $Δm^2_{21}$ open a new avenue for probing flavor symmetric structures in the lepton sector. Motivated by this, we study a model in which $μ-τ$ reflection symmetry naturally emerges from an underlying $A_4$ flavor symmetry within a type-II seesaw framework. Beyond its standard predictions of $θ_{23}=45^{\circ}$ and $δ_{\rm CP}=\pm π/2$, the framework yields testable predictions for $θ_{12}$ that can be probed by JUNO. Two viable scenarios arise, one predicting $\sin^2θ_{12} \gsim 0.335$, which is strongly disfavored by the latest JUNO results. Correlations between $θ_{12}$ and model parameters further enhance the model's predictivity. Future measurements at DUNE and T2HK will provide complementary tests of this scenario.

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Ranjeet Kumar. 2026-05-08. Fate of $θ_{12}$ under $μ-τ$ Reflection Symmetry in Light of the First JUNO Results. https://doi.org/10.1103/1x8b-p916

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