Updated fit to three neutrino mixing: exploring the accelerator-reactor complementarity

TL;DR

This paper updates the global fit of three-neutrino oscillation parameters using 2016 data, highlighting the current uncertainties in mass ordering, CP violation, and mixing angles, and emphasizing the complementarity of accelerator and reactor experiments.

Contribution

It provides the latest combined analysis of neutrino oscillation data, including a Monte Carlo study of parameter confidence levels and the impact of accelerator-reactor data integration.

Findings

Mass ordering sensitivity below 1σ

Maximal θ23 mixing allowed at >90% CL

Best fit CP phase around 270°

Abstract

We perform a combined fit to global neutrino oscillation data available as of fall 2016 in the scenario of three-neutrino oscillations and present updated allowed ranges of the six oscillation parameters. We discuss the differences arising between the consistent combination of the data samples from accelerator and reactor experiments compared to partial combinations. We quantify the confidence in the determination of the less precisely known parameters $\theta_{23}$, $\delta_\text{CP}$, and the neutrino mass ordering by performing a Monte Carlo study of the long baseline accelerator and reactor data. We find that the sensitivity to the mass ordering and the $\theta_{23}$ octant is below $1\sigma$. Maximal $\theta_{23}$ mixing is allowed at slightly more than 90% CL. The best fit for the CP violating phase is around $270^\circ$, CP conservation is allowed at slightly above $1\sigma$, and values of $\delta_\text{CP} \simeq 90^\circ$ are disfavored at around 99% CL for normal ordering and higher CL for inverted ordering.