Z. M. Wang

TL;DR: The Jiangmen Underground Neutrino Observatory (JUNO) as discussed by the authors was proposed to determine the neutrino mass hierarchy using an underground liquid scintillator detector.

Abstract: A measurement of electron antineutrino oscillation by the Daya Bay Reactor Neutrino Experiment is described in detail. Six 2.9-GWth nuclear power reactors of the Daya Bay and Ling Ao nuclear power facilities served as intense sources of νe’s. Comparison of the νe rate and energy spectrum measured by antineutrino detectors far from the nuclear reactors (∼1500–1950 m ) relative to detectors near the reactors (∼350–600 m ) allowed a precise measurement of νe disappearance. More than 2.5 million νe inverse beta-decay interactions were observed, based on the combination of 217 days of operation of six antineutrino detectors (December, 2011–July, 2012) with a subsequent 1013 days using the complete configuration of eight detectors (October, 2012–July, 2015). The νe rate observed at the far detectors relative to the near detectors showed a significant deficit, R=0.949±0.002(stat)±0.002(syst). The energy dependence of νe disappearance showed the distinct variation predicted by neutrino oscillation. Analysis using an approximation for the three-flavor oscillation probability yielded the flavor-mixing angle sin^2 2θ_(13)=0.0841±0.0027(stat)±0.0019(syst) and the effective neutrino mass-squared difference of |Δm^2_(ee)|=(2.50±0.06(stat)±0.06(syst))×10^(−3) eV^2. Analysis using the exact three-flavor probability found Δm^2_(32)=(2.45±0.06(stat)±0.06(syst))×10^(−3) eV^2 assuming the normal neutrino mass hierarchy and Δm^2_(32)=(−2.56±0.06(stat)±0.06(syst))×10^(−3) eV^2 for the inverted hierarchy.

TL;DR: This Letter reports the first extraction of individual antineutrino spectra from ^{235}U and ^{239}Pu fission and an improved measurement of the prompt energy spectrum of reactor anteutrinos at Daya Bay, and the shape of the measured inverse beta-decay Prompt energy spectrum disagrees with the prediction of the Huber-Mueller model.

TL;DR: In this paper, a 20 t liquid scintillator (LS) sample was produced in a pilot plant at Daya Bay, and the optical properties of the new LS in various compositions were studied by replacing the gadolinium-loaded LS in one antineutrino detector.