Testable constraint on near-tribimaximal neutrino mixing

TL;DR

This paper derives a testable constraint on deviations from tribimaximal neutrino mixing, showing that large deviations in atmospheric mixing and CP violation cannot occur simultaneously at lowest order, guiding future experimental verification.

Contribution

It provides an analytical relation linking measurable deviations in neutrino mixing angles and CP violation within a perturbative framework from the TBM limit.

Findings

Large deviations in atmospheric mixing and CP violation are mutually exclusive at lowest order.

The derived relation offers a testable prediction for upcoming neutrino experiments.

Deviations are constrained to be within 12-17%, challenging experimental verification.

Abstract

General lowest order perturbations to hermitian squared mass matrices of leptons are considered away from the tribimaximal (TBM) limit in which a weak flavor basis with mass diagonal charged leptons is chosen. The three measurable TBM deviants are expressed linearly in terms of perturbation induced dimensionless coefficients appearing in the charged lepton and neutrino flavor eigenstates. With unnatural cancellations assumed to be absent and the charged lepton perturbation contributions to their flavor eigenstates argued to be small, we analytically derive the following result. Within lowest order perturbations, a deviation from maximal atmospheric neutrino mixing and the amount of CP violation in neutrino oscillations cannot both be large (i.e. $12$-$17 \% $), posing the challenge of verification to forthcoming experiments at the intensity frontier.