First Measurement of High-Energy Reactor Antineutrinos at Daya Bay

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2022-07-18, 2022-07-18
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This Letter reports the first measurement of high-energy reactor antineutrinos at Daya Bay, with nearly 9000 inverse beta decay candidates in the prompt energy region of 8-12 MeV observed over 1958 days of data collection. A multivariate analysis is used to separate 2500 signal events from background statistically. The hypothesis of no reactor antineutrinos with neutrino energy above 10 MeV is rejected with a significance of 6.2 standard deviations. A 29% antineutrino flux deficit in the prompt energy region of 8-11 MeV is observed compared to a recent model prediction. We provide the unfolded antineutrino spectrum above 7 MeV as a data-based reference for other experiments. This result provides the first direct observation of the production of antineutrinos from several high-Qβ isotopes in commercial reactors.

Science & Technology, Physical Sciences, Physics, Multidisciplinary, Physics, NEUTRON FISSION-PRODUCTS, BETA-DECAY, EMISSION, SPECTRA, PU-239, Daya Bay Collaboration, 5106 Nuclear and Plasma Physics, 5107 Particle and High Energy Physics, 5110 Synchrotrons and Accelerators, 51 Physical Sciences, 7 Affordable and Clean Energy, 40 Engineering, 49 Mathematical sciences