Measurement of electron antineutrino oscillation based on 1230 days of operation of the Daya Bay experiment
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.
© 2017 American Physical Society. Received 31 October 2016; published 6 April 2017. Daya Bay is supported in part by the Ministry of Science and Technology of China; the U.S. Department of Energy; the Chinese Academy of Sciences; the Chinese Academy of Science (CAS) Center for Excellence in Particle Physics; the National Natural Science Foundation of China; the Guangdong provincial government; the Shenzhen municipal government; the China Guangdong Nuclear Power Group; Key Laboratory of Particle and Radiation Imaging (Tsinghua University); the Ministry of Education, Key Laboratory of Particle Physics and Particle Irradiation (Shandong University); the Ministry of Education, Shanghai Laboratory for Particle Physics and Cosmology; the Research Grants Council of the Hong Kong Special Administrative Region of China; the University Development Fund of the University of Hong Kong; the Ministry of Education (MOE) program for Research of Excellence at National Taiwan University, National Chiao-Tung University, and the National Science Council (NSC) fund support from Taiwan; the U.S. National Science Foundation; the Alfred P. Sloan Foundation; the Ministry of Education, Youth, and Sports of the Czech Republic; the Joint Institute of Nuclear Research in Dubna, Russia; the Russian Foundation for Basic Research (RFBR) research program; the National Commission of Scientific and Technological Research of Chile; and the Tsinghua University Initiative Scientific Research Program. We acknowledge Yellow River Engineering Consulting Co., Ltd., and China Railway 15th Bureau Group Co., Ltd., for building the underground laboratory. We are grateful for the ongoing cooperation from the China General Nuclear Power Group and China Light and Power Company.
Submitted - 1610.04802.pdf
Supplemental Material - DayaBay_Oscillation_1230days_supplemental.zip
Published - PhysRevD.95.072006.pdf