First measurement of high-energy reactor antineutrinos at Daya Bay

Abstract

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-$Q_{\beta }$ isotopes in commercial reactors.

7 pages, 4 figures, accepted by Physical Review Letters

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• The Reactor Antineutrino Anomaly
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• Total Absorption Gamma-Ray Spectroscopy of 87Br, 88Br and 94Rb Beta-Delayed Neutron Emitters
• Beta-decay studies for applied and basic nuclear physics
• Antineutrino Energy Spectrum Unfolding Based on the Daya Bay Measurement and Its Applications
• First antineutrino energy spectrum from ${}^{235}$U fissions with the STEREO detector at ILL
• Accurate Measurement of the Electron Antineutrino Yield of U-235 Fissions from the STEREO Experiment with 119 Days of Reactor-On Data
• Joint Measurement of the ${}^{235}$U Antineutrino Spectrum by Prospect and Stereo

Cited by in corpus (6)

• Direct observation of coherent elastic antineutrino-nucleus scattering
• Final CONUS results on coherent elastic neutrino-nucleus scattering at the Brokdorf reactor
• Reactor antineutrino flux and anomaly
• New constraints on coherent elastic neutrino-nucleus scattering by the nuGeN experiment
• Exploring Current Constraints on Antineutrino Production by ${}^{241}$Pu and Paths Towards the Precision Reactor Flux Era
• Testing lepton non-unitarity with the next generation of Germanium-based CE$\nu$NS reactor experiments