/ physics.ins-det arXiv:1704.01082


Evolution of the Reactor Antineutrino Flux and Spectrum at Daya Bay


An, F.P. (East China U. Sci. Tech., Shanghai) ; Balantekin, A.B. (U. Wisconsin, Madison (main)) ; Band, H.R. (Yale U.) ; Bishai, M. (Brookhaven) ; Blyth, S. (Natl. United U., Taiwan) ; Cao, D. (Nanjing U.) ; Cao, G.F. (Beijing, Inst. High Energy Phys.) ; Cao, J. (Beijing, Inst. High Energy Phys.) ; Chan, Y.L. (Hong Kong, Chinese U.) ; Chang, J.F. (Beijing, Inst. High Energy Phys.) ; Chang, Y. (Natl. United U., Taiwan) ; Chen, H.S. (Beijing, Inst. High Energy Phys.) ; Chen, Q.Y. (Shandong U.) ; Chen, S.M. (Tsinghua U., Beijing) ; Chen, Y.X. (Peking U.) ; Chen, Y. (Shenzhen U.) ; Cheng, J. (Shandong U.) ; Cheng, Z.K. (Zhongshan U.) ; Cherwinka, J.J. (U. Wisconsin, Madison (main)) ; Chu, M.C. (Hong Kong, Chinese U.) ; Chukanov, A. (Dubna, JINR) ; Cummings, J.P. (Siena Coll., Loudonville) ; Ding, Y.Y. (Beijing, Inst. High Energy Phys.) ; Diwan, M.V. (Brookhaven) ; Dolgareva, M. (Dubna, JINR) ; Dove, J. (Illinois U., Urbana) ; Dwyer, D.A. (LBL, Berkeley) ; Edwards, W.R. (LBL, Berkeley) ; Gill, R. (Brookhaven) ; Gonchar, M. (Dubna, JINR) ; Gong, G.H. (Tsinghua U., Beijing) ; Gong, H. (Tsinghua U., Beijing) ; Grassi, M. (Beijing, Inst. High Energy Phys.) ; Gu, W.Q. (Shanghai, Jiao Tong U.) ; Guo, L. (Tsinghua U., Beijing) ; Guo, X.H. (Beijing Normal U.) ; Guo, Y.H. (Xian Jiaotong U.) ; Guo, Z. (Tsinghua U., Beijing) ; Hackenburg, R.W. (Brookhaven) ; Hans, S. (Beijing, Inst. High Energy Phys.) ; He, M. (Beijing, Inst. High Energy Phys.) ; Heeger, K.M. (Yale U.) ; Heng, Y.K. (Beijing, Inst. High Energy Phys.) ; Higuera, A. (Houston U.) ; Hsiung, Y.B. (Taiwan, Natl. Taiwan U.) ; Hu, B.Z. (Taiwan, Natl. Taiwan U.) ; Hu, T. (Beijing, Inst. High Energy Phys.) ; Huang, E.C. (Illinois U., Urbana) ; Huang, H.X. (Beijing, Inst. Atomic Energy) ; Huang, X.T. (Shandong U.) ; Huang, Y.B. (Beijing, Inst. High Energy Phys.) ; Huber, P. (Virginia Tech.) ; Huo, W. (Hefei, CUST) ; Hussain, G. (Tsinghua U., Beijing) ; Jaffe, D.E. (Brookhaven) ; Jen, K.L. (Taiwan, Natl. Chiao Tung U.) ; Ji, X.P. (Nankai U.) ; Ji, X.L. (Beijing, Inst. High Energy Phys.) ; Jiao, J.B. (Shandong U.) ; Johnson, R.A. (Cincinnati U.) ; Jones, D. (Temple U.) ; Kang, L. (DongGuan U. Technol.) ; Kettell, S.H. (Brookhaven) ; Khan, A. (Zhongshan U.) ; Kohn, S. (UC, Berkeley) ; Kramer, M. (LBL, Berkeley) ; Kwan, K.K. (Hong Kong, Chinese U.) ; Kwok, M.W. (Hong Kong, Chinese U.) ; Langford, T.J. (Yale U.) ; Lau, K. (Houston U.) ; Lebanowski, L. (Tsinghua U., Beijing) ; Lee, J. (LBL, Berkeley) ; Lee, J.H.C. (Hong Kong U.) ; Lei, R.T. (DongGuan U. Technol.) ; Leitner, R. (Charles U.) ; Leung, J.K.C. (Hong Kong U.) ; Li, C. (Shandong U.) ; Li, D.J. (Hefei, CUST) ; Li, F. (Beijing, Inst. High Energy Phys.) ; Li, G.S. (Shanghai, Jiao Tong U.) ; Li, Q.J. (Beijing, Inst. High Energy Phys.) ; Li, S. (DongGuan U. Technol.) ; Li, S.C. (Virginia Tech.) ; Li, W.D. (Beijing, Inst. High Energy Phys.) ; Li, X.N. (Beijing, Inst. High Energy Phys.) ; Li, X.Q. (Nankai U.) ; Li, Y.F. (Beijing, Inst. High Energy Phys.) ; Li, Z.B. (Zhongshan U.) ; Liang, H. (Hefei, CUST) ; Lin, C.J. (LBL, Berkeley) ; Lin, G.L. (Taiwan, Natl. Chiao Tung U.) ; Lin, S. (DongGuan U. Technol.) ; Lin, S.K. (Houston U.) ; Lin, Y.-C. (Taiwan, Natl. Taiwan U.) ; Ling, J.J. (Zhongshan U.) ; Link, J.M. (Virginia Tech.) ; Littenberg, L. (Brookhaven) ; Littlejohn, B.R. (IIT, Chicago) ; Liu, J.L. (Shanghai, Jiao Tong U.) ; Liu, J.C. (Beijing, Inst. High Energy Phys.) ; Loh, C.W. (Nanjing U.) ; Lu, C. (Princeton U.) ; Lu, H.Q. (Beijing, Inst. High Energy Phys.) ; Lu, J.S. (Beijing, Inst. High Energy Phys.) ; Luk, K.B. (UC, Berkeley) ; Ma, X.Y. (Beijing, Inst. High Energy Phys.) ; Ma, X.B. (Peking U.) ; Ma, Y.Q. (Beijing, Inst. High Energy Phys.) ; Malyshkin, Y. (Chile U., Catolica) ; Martinez Caicedo, D.A. (IIT, Chicago) ; McDonald, K.T. (Princeton U.) ; McKeown, R.D. (Caltech) ; Mitchell, I. (Houston U.) ; Nakajima, Y. (LBL, Berkeley) ; Napolitano, J. (Temple U.) ; Naumov, D. (Dubna, JINR) ; Naumova, E. (Dubna, JINR) ; Ngai, H.Y. (Hong Kong U.) ; Ochoa-Ricoux, J.P. (Chile U., Catolica) ; Olshevskiy, A. (Dubna, JINR) ; Pan, H.-R. (Taiwan, Natl. Taiwan U.) ; Park, J. (Virginia Tech.) ; Patton, S. (LBL, Berkeley) ; Pec, V. (Charles U.) ; Peng, J.C. (Illinois U., Urbana) ; Pinsky, L. (Houston U.) ; Pun, C.S.J. (Hong Kong U.) ; Qi, F.Z. (Beijing, Inst. High Energy Phys.) ; Qi, M. (Nanjing U.) ; Qian, X. (Brookhaven) ; Qiu, R.M. (Peking U.) ; Raper, N. (Rensselaer Poly.) ; Ren, J. (Beijing, Inst. Atomic Energy) ; Rosero, R. (Brookhaven) ; Roskovec, B. (Charles U.) ; Ruan, X.C. (Beijing, Inst. Atomic Energy) ; Steiner, H. (UC, Berkeley) ; Stoler, P. (Rensselaer Poly.) ; Sun, J.L. (CGNPC, Shenzhen) ; Tang, W. (Brookhaven) ; Taychenachev, D. (Dubna, JINR) ; Treskov, K. (Dubna, JINR) ; Tsang, K.V. (LBL, Berkeley) ; Tull, C.E. (LBL, Berkeley) ; Viaux, N. (Chile U., Catolica) ; Viren, B. (Brookhaven) ; Vorobel, V. (Charles U.) ; Wang, C.H. (Natl. United U., Taiwan) ; Wang, M. (Shandong U.) ; Wang, N.Y. (Beijing Normal U.) ; Wang, R.G. (Beijing, Inst. High Energy Phys.) ; Wang, W. (William-Mary Coll.) ; Wang, X. (Natl. U. Defense Tech., Hunan) ; Wang, Y.F. (Beijing, Inst. High Energy Phys.) ; Wang, Z. (Tsinghua U., Beijing) ; Wang, Z. (Beijing, Inst. High Energy Phys.) ; Wang, Z.M. (Beijing, Inst. High Energy Phys.) ; Wei, H.Y. (Tsinghua U., Beijing) ; Wen, L.J. (Beijing, Inst. High Energy Phys.) ; Whisnant, K. (Iowa State U.) ; White, C.G. (IIT, Chicago) ; Whitehead, L. (Houston U.) ; Wise, T. (Yale U.) ; Wong, H.L.H. (UC, Berkeley) ; Wong, S.C.F. (Zhongshan U.) ; Worcester, E. (Brookhaven) ; Wu, C.-H. (Taiwan, Natl. Chiao Tung U.) ; Wu, Q. (Shandong U.) ; Wu, W.J. (Beijing, Inst. High Energy Phys.) ; Xia, D.M. (Chongqing U.) ; Xia, J.K. (Beijing, Inst. High Energy Phys.) ; Xing, Z.Z. (Beijing, Inst. High Energy Phys.) ; Xu, J.L. (Beijing, Inst. High Energy Phys.) ; Xu, Y. (Zhongshan U.) ; Xue, T. (Tsinghua U., Beijing) ; Yang, C.G. (Beijing, Inst. High Energy Phys.) ; Yang, H. (Nanjing U.) ; Yang, L. (DongGuan U. Technol.) ; Yang, M.S. (Beijing, Inst. High Energy Phys.) ; Yang, M.T. (Shandong U.) ; Yang, Y.Z. (Zhongshan U.) ; Ye, M. (Beijing, Inst. High Energy Phys.) ; Ye, Z. (Houston U.) ; Yeh, M. (Brookhaven) ; Young, B.L. (Iowa State U.) ; Yu, Z.Y. (Beijing, Inst. High Energy Phys.) ; Zeng, S. (Beijing, Inst. High Energy Phys.) ; Zhan, L. (Beijing, Inst. High Energy Phys.) ; Zhang, C. (Brookhaven) ; Zhang, C.C. (Beijing, Inst. High Energy Phys.) ; Zhang, H.H. (Zhongshan U.) ; Zhang, J.W. (Beijing, Inst. High Energy Phys.) ; Zhang, Q.M. (Xian Jiaotong U.) ; Zhang, R. (Nanjing U.) ; Zhang, X.T. (Beijing, Inst. High Energy Phys.) ; Zhang, Y.M. (Tsinghua U., Beijing) ; Zhang, Y.X. (CGNPC, Shenzhen) ; Zhang, Y.M. (Zhongshan U.) ; Zhang, Z.J. (DongGuan U. Technol.) ; Zhang, Z.Y. (Beijing, Inst. High Energy Phys.) ; Zhang, Z.P. (Hefei, CUST) ; Zhao, J. (Beijing, Inst. High Energy Phys.) ; Zhou, L. (Beijing, Inst. High Energy Phys.) ; Zhuang, H.L. (Beijing, Inst. High Energy Phys.) ; Zou, J.H. (Beijing, Inst. High Energy Phys.)

Published in: Phys.Rev.Lett.
Pages: 7

Abstract: The Daya Bay experiment has observed correlations between reactor core fuel evolution and changes in the reactor antineutrino flux and energy spectrum. Four antineutrino detectors in two experimental halls were used to identify 2.2 million inverse beta decays (IBDs) over 1230 days spanning multiple fuel cycles for each of six 2.9 GW$_{\textrm{th}}$ reactor cores at the Daya Bay and Ling Ao nuclear power plants. Using detector data spanning effective $^{239}$Pu fission fractions, $F_{239}$, from 0.25 to 0.35, Daya Bay measures an average IBD yield, $\bar{\sigma}_f$, of $(5.90 \pm 0.13) \times 10^{-43}$ cm$^2$/fission and a fuel-dependent variation in the IBD yield, $d\sigma_f/dF_{239}$, of $(-1.86 \pm 0.18) \times 10^{-43}$ cm$^2$/fission. This observation rejects the hypothesis of a constant antineutrino flux as a function of the $^{239}$Pu fission fraction at 10 standard deviations. The variation in IBD yield was found to be energy-dependent, rejecting the hypothesis of a constant antineutrino energy spectrum at 5.1 standard deviations. While measurements of the evolution in the IBD spectrum show general agreement with predictions from recent reactor models, the measured evolution in total IBD yield disagrees with recent predictions at 3.1$\sigma$. This discrepancy indicates that an overall deficit in measured flux with respect to predictions does not result from equal fractional deficits from the primary fission isotopes $^{235}$U, $^{239}$Pu, $^{238}$U, and $^{241}$Pu. Based on measured IBD yield variations, yields of $(6.17 \pm 0.17)$ and $(4.27 \pm 0.26) \times 10^{-43}$ cm$^2$/fission have been determined for the two dominant fission parent isotopes $^{235}$U and $^{239}$Pu. A 7.8% discrepancy between the observed and predicted $^{235}$U yield suggests that this isotope may be the primary contributor to the reactor antineutrino anomaly.

Web-Page: http://inspirehep.net/record/1589439/files/figures_fig5.png; http://inspirehep.net/record/1589439/files/figures_fig2.png; http://inspirehep.net/record/1589439/files/figures_fig3.png; http://inspirehep.net/record/1589439/files/figures_fig1.png; http://inspirehep.net/record/1589439/files/figures_fig4.png; http://inspirehep.net/record/1589439/files/arXiv:1704.01082.pdf


Note: 7 pages, 5 figures; submitted to Phys. Rev. Lett

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