Global oscillation data analysis on the $3\nu$ mixing without unitarity

TL;DR

This paper analyzes neutrino oscillation data without assuming unitarity in the 3-neutrino mixing matrix, finding current data consistent with the standard model but highlighting areas for improved precision in future experiments.

Contribution

It provides the first comprehensive constraints on the neutrino mixing matrix without unitarity assumptions using recent experimental data.

Findings

Current data are consistent with the standard 3ν scheme.

Precision on matrix elements can reach a few percent at 3σ CL.

Deviations from unitarity are confined within small bounds.

Abstract

We present results of a combined analysis in neutrino oscillations without unitarity assumption in the $3\nu$ mixing picture. Constraints on neutrino mixing matrix elements are based on recent data from the reactor, solar and long-baseline accelerator neutrino oscillation experiments. The current data are consistent with the standard $3\nu$ scheme. The precision on different matrix elements can be as good as a few percent at $3\sigma$ CL, and is mainly limited by the experimental statistical uncertainty. The $\nu_e$ related elements are the most precisely measured among all sectors with the uncertainties $<20\%$. The measured leptonic CP violation is very close to the one assuming the standard $3\nu$ mixing. The deviations on normalization and the unitarity triangle closure are confined within $\mathcal{O}(10^{-3})$, $\mathcal{O}(10^{-2})$ and $\mathcal{O}(10^{-1})$, for $\nu_e$, $\nu_{\mu}$ and $\nu_{\tau}$ sectors, respectively. We look forward to the next-generation neutrino oscillation experiments \textit{such as} DUNE, T2HK, and JUNO, especially the precise measurements on $\nu_\tau$ oscillations, to significantly improve the precision of unitarity test on the $3\nu$ mixing matrix.