Improved Measurement of Electron Antineutrino Disappearance at Daya Bay

TL;DR

This paper presents an improved measurement of the neutrino mixing angle θ13 using data from the Daya Bay Reactor Neutrino Experiment, significantly excluding zero and refining its value with high statistical confidence.

Contribution

The study provides the most precise measurement of θ13 to date, utilizing multiple detectors and extensive data to reduce uncertainties and improve the understanding of neutrino oscillations.

Findings

Excludes zero θ13 with 7.7σ significance.

Measures sin^2 2θ13 = 0.089 ± 0.010 (stat.) ± 0.005 (syst.).

Observed antineutrino deficit consistent with oscillations.

Abstract

We report an improved measurement of the neutrino mixing angle $\theta_{13}$ from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for $\sin^22\theta_{13}$ with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GW$_{\rm th}$ were detected in six antineutrino detectors deployed in two near (flux-weighted baselines of 470 m and 576 m) and one far (1648 m) underground experimental halls. Using 139 days of data, 28909 (205308) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is $0.944\pm 0.007({\rm stat.}) \pm 0.003({\rm syst.})$. An analysis of the relative rates in six detectors finds $\sin^22\theta_{13}=0.089\pm 0.010({\rm stat.})\pm0.005({\rm syst.})$ in a three-neutrino framework.