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

TLDR

The study performs a combined fit of global neutrino oscillation data (as of fall 2016) within the three‑neutrino framework to update the allowed ranges of the six oscillation parameters. The analysis consistently combines accelerator and reactor data, contrasts this with partial combinations, and uses a Monte Carlo study of long‑baseline accelerator and reactor data to quantify confidence in the less precisely known parameters θ₂₃, δ_CP, and the mass ordering. The fit shows that sensitivity to the mass ordering and θ₂₃ octant is below 1σ, maximal θ₂₃ mixing is allowed at >90 % CL, the best‑fit CP‑violating phase is ≈270°, CP conservation is allowed at just over 1σ, and δ_CP≈90° is disfavored at ≈99 % CL for normal ordering (and at higher CL for inverted ordering).

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.