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Published September 13, 2019 | Submitted + Published
Journal Article Open

Extraction of the ^(235)U and ^(239)Pu Antineutrino Spectra at Daya Bay

Abstract

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 antineutrinos at Daya Bay. The analysis uses 3.5×10^6 inverse beta-decay candidates in four near antineutrino detectors in 1958 days. The individual antineutrino spectra of the two dominant isotopes, ^(235)U and ^(239)Pu, are extracted using the evolution of the prompt spectrum as a function of the isotope fission fractions. In the energy window of 4–6 MeV, a 7% (9%) excess of events is observed for the ^(235)U (^(239)Pu) spectrum compared with the normalized Huber-Mueller model prediction. The significance of discrepancy is 4.0σ for ^(235)U spectral shape compared with the Huber-Mueller model prediction. The shape of the measured inverse beta-decay prompt energy spectrum disagrees with the prediction of the Huber-Mueller model at 5.3σ. In the energy range of 4–6 MeV, a maximal local discrepancy of 6.3σ is observed.

Additional Information

© 2019 Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3. Received 16 April 2019; revised manuscript received 4 August 2019; published 13 September 2019. This work was supported in part by the Ministry of Science and Technology of China, the U.S. Department of Energy, the Chinese Academy of Sciences, the CAS Center for Excellence in Particle Physics, the National Natural Science Foundation of China, the Guangdong Provincial Government, the Shenzhen Municipal Government, the China General Nuclear Power Group, the Research Grants Council of the Hong Kong Special Administrative Region of China, the Ministry of Education in Taiwan, the U.S. National Science Foundation, the Ministry of Education, Youth, and Sports of the Czech Republic, the Charles University Research Centre UNCE, the Joint Institute of Nuclear Research in Dubna, Russia, the National Commission of Scientific and Technological Research of Chile. 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 Guangdong Nuclear Power Group and China Light & Power Company.

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Published - PhysRevLett.123.111801.pdf

Submitted - 1904.07812.pdf

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Additional details

Created:
August 19, 2023
Modified:
October 18, 2023