Non-unitary deviation from the tri-bimaximal lepton mixing and its implications on neutrino oscillations

TL;DR

This paper introduces a new neutrino mixing pattern involving non-unitary corrections, affecting neutrino oscillation probabilities and CP violation, with implications for experimental detection and theoretical models.

Contribution

It proposes a novel parametrization of the neutrino mixing matrix incorporating non-unitary effects and provides formulas for oscillation probabilities in this framework.

Findings

Non-unitary effects can significantly alter neutrino oscillation probabilities.

Small non-unitary perturbations and CP phases can be potentially measured experimentally.

Deformed unitarity triangles offer a new way to analyze CP violation in neutrino physics.

Abstract

We propose a new pattern of the neutrino mixing matrix which can be parametrized as the product of an arbitrary Hermitian matrix and the well-known tri-bimaximal mixing matrix. In this scenario, nontrivial values of the smallest neutrino mixing angle \theta_13 and the CP-violating phases entirely arise from the non-unitary corrections. We present a complete set of series expansion formulas for neutrino oscillation probabilities both in vacuum and in matter of constant density. We do a numerical analysis to show the non-unitary effects on neutrino oscillations. The possibility of determining small non-unitary perturbations and CP-violating phases is discussed by measuring neutrino oscillation probabilities and constructing "deformed unitarity triangles". Some brief comments on the non-unitary neutrino mixing matrix in the type-II seesaw models are also given.