Constraining the Neutrino Mixing Matrix via Single-Sector Charged-Lepton Rotations in the JUNO Precision Era

TL;DR

This paper explores how precise measurements of the PMNS matrix, especially from JUNO, constrain the neutrino mass matrix structure assuming simple charged-lepton rotations, providing analytical relations.

Contribution

It introduces a framework linking charged-lepton rotations to neutrino mixing, deriving sum-rule formulas using the latest JUNO data for the first time.

Findings

Constraints on the neutrino mass matrix from single-sector charged-lepton rotations.

Analytical sum-rule expressions relating PMNS parameters to underlying matrices.

Enhanced understanding of flavor symmetries in neutrino physics.

Abstract

The unprecedented precision now being achieved in the measurement of the Pontecorvo--Maki--Nakagawa--Sakata (PMNS) lepton mixing matrix opens a new window onto the underlying structure of the neutrino mass matrix and the possibly associated flavor symmetries. In this work, we investigate the constraints imposed on the unitary matrix $U_\nu$ that diagonalises the neutrino mass matrix, under the hypothesis that the charged-lepton mixing matrix $U_l$ consists of a single two-by-two rotation in one of the three sectors: (1,2), (1,3), or (2,3). For this analysis, we considered the latest global fit which incorporates the precision measurement of $\theta_{12}$ from the JUNO experiment. For each scenario, we also derive analytical expressions for the entries of $U_\nu$ in terms of the measured PMNS parameters to obtain compact sum-rule-like formulae.