First measurement of high-energy reactor antineutrinos at Daya Bay

• Published in: arXiv.org 2022-07
• Main Authors: Daya Bay collaboration, An, F P, Chang, J F, Chang, Y, Chen, H S, Chen, S M, Chen, Y X, Cheng, J, Cherwinka, J J, Dohnal, T, Dove, J, Dwyer, D A, Gallo, J P, Guo, L, Guo, X H, Guo, Y H, Guo, Z, Hackenburg, R W, Heeger, K M, Heng, Y K, Hor, Y K, T Hu, Huber, P, Jen, K L, Ji, X L, Ji, X P, Johnson, R A, Jones, D, Kang, L, Kettell, S H, Kohn, S, Langford, T J, Lee, J, Lee, J H C, Li, Q J, S Li, Li, Y F, Liang, H, Ling, J J, Littlejohn, B R, Liu, J L, C Lu, Lu, J S, Ma, X B, Ma, Y Q, Marshall, C, McKeown, R D, Meng, Y, Naumov, D, Ochoa-Ricoux, J P, Patton, S, Peng, J C, Pun, C S J, M Qi, Ren, J, C Morales Reveco, Ruan, X C, Sun, J L, Tmej, T, Treskov, K, Tull, C E, Viren, B, Wang, C H, Wang, J, Wang, M, Wang, W, Wang, X, Wang, Y, Wei, H Y, Wen, L J, White, C G, Wong, H L H, Wu, D R, Q Wu, Wu, W J, Xie, Z Q, Xing, Z Z, Xu, J L, T Xu, Xue, T, Yang, L, Yao, H F, Young, B L, Yu, H Z, Yu, Z Y, Zeng, S, Zeng, Y, Zhan, L, Zhang, C, Zhang, H H, Zhang, J W, Zhang, X T, Zhang, Y M, Zhang, Y Y, Zhang, Z J, Zhang, Z P, Zhang, Z Y, Zhao, J, Zhou, L, Zou, J H
• Format: Article
• Language: English
• Subjects: Antineutrinos; Beta decay; Data collection; Multivariate analysis
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2203.06686

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.