Observation of Reactor Electron Antineutrinos Disappearance in the RENO Experiment

TLDR

The RENO experiment measured reactor antineutrinos with two identical detectors at 294 m and 1383 m from six 2.8 GW(th) reactors over 229 days, recording 17,102 far‑detector and 154,088 near‑detector candidate events with background fractions of 5.5 % and 2.7 %. The experiment observed a 4.9‑σ deficit of reactor antineutrinos, with a far‑detector ratio of 0.920±0.009(stat)±0.014(syst) and a measured mixing angle sin²2θ₁₃=0.113±0.013(stat)±0.019(syst).

Abstract

The RENO experiment has observed the disappearance of reactor electron antineutrinos, consistent with neutrino oscillations, with a significance of 4.9 standard deviations. Antineutrinos from six 2.8 GW(th) reactors at the Yonggwang Nuclear Power Plant in Korea, are detected by two identical detectors located at 294 and 1383 m, respectively, from the reactor array center. In the 229 d data-taking period between 11 August 2011 and 26 March 2012, the far (near) detector observed 17102 (154088) electron antineutrino candidate events with a background fraction of 5.5% (2.7%). The ratio of observed to expected numbers of antineutrinos in the far detector is 0.920±0.009(stat)±0.014(syst). From this deficit, we determine sin(2)2θ(13)=0.113±0.013(stat)±0.019(syst) based on a rate-only analysis.