大亚湾反应堆反中微子通量与能谱的演化
Evolution of the Reactor Antineutrino Flux and Spectrum at Daya Bay.
作者信息
An F P, Balantekin A B, Band H R, Bishai M, Blyth S, Cao D, Cao G F, Cao J, Chan Y L, Chang J F, Chang Y, Chen H S, Chen Q Y, Chen S M, Chen Y X, Chen Y, Cheng J, Cheng Z K, Cherwinka J J, Chu M C, Chukanov A, Cummings J P, Ding Y Y, Diwan M V, Dolgareva M, Dove J, Dwyer D A, Edwards W R, Gill R, Gonchar M, Gong G H, Gong H, Grassi M, Gu W Q, Guo L, Guo X H, Guo Y H, Guo Z, Hackenburg R W, Hans S, He M, Heeger K M, Heng Y K, Higuera A, Hsiung Y B, Hu B Z, Hu T, Huang E C, Huang H X, Huang X T, Huang Y B, Huber P, Huo W, Hussain G, Jaffe D E, Jen K L, Ji X P, Ji X L, Jiao J B, Johnson R A, Jones D, Kang L, Kettell S H, Khan A, Kohn S, Kramer M, Kwan K K, Kwok M W, Langford T J, Lau K, Lebanowski L, Lee J, Lee J H C, Lei R T, Leitner R, Leung J K C, Li C, Li D J, Li F, Li G S, Li Q J, Li S, Li S C, Li W D, Li X N, Li X Q, Li Y F, Li Z B, Liang H, Lin C J, Lin G L, Lin S, Lin S K, Lin Y-C, Ling J J, Link J M, Littenberg L, Littlejohn B R, Liu J L, Liu J C, Loh C W, Lu C, Lu H Q, Lu J S, Luk K B, Ma X Y, Ma X B, Ma Y Q, Malyshkin Y, Martinez Caicedo D A, McDonald K T, McKeown R D, Mitchell I, Nakajima Y, Napolitano J, Naumov D, Naumova E, Ngai H Y, Ochoa-Ricoux J P, Olshevskiy A, Pan H-R, Park J, Patton S, Pec V, Peng J C, Pinsky L, Pun C S J, Qi F Z, Qi M, Qian X, Qiu R M, Raper N, Ren J, Rosero R, Roskovec B, Ruan X C, Steiner H, Stoler P, Sun J L, Tang W, Taychenachev D, Treskov K, Tsang K V, Tull C E, Viaux N, Viren B, Vorobel V, Wang C H, Wang M, Wang N Y, Wang R G, Wang W, Wang X, Wang Y F, Wang Z, Wang Z, Wang Z M, Wei H Y, Wen L J, Whisnant K, White C G, Whitehead L, Wise T, Wong H L H, Wong S C F, Worcester E, Wu C-H, Wu Q, Wu W J, Xia D M, Xia J K, Xing Z Z, Xu J L, Xu Y, Xue T, Yang C G, Yang H, Yang L, Yang M S, Yang M T, Yang Y Z, Ye M, Ye Z, Yeh M, Young B L, Yu Z Y, Zeng S, Zhan L, Zhang C, Zhang C C, Zhang H H, Zhang J W, Zhang Q M, Zhang R, Zhang X T, Zhang Y M, Zhang Y X, Zhang Y M, Zhang Z J, Zhang Z Y, Zhang Z P, Zhao J, Zhou L, Zhuang H L, Zou J H
机构信息
Institute of Modern Physics, East China University of Science and Technology, Shanghai.
University of Wisconsin, Madison, Wisconsin 53706.
出版信息
Phys Rev Lett. 2017 Jun 23;118(25):251801. doi: 10.1103/PhysRevLett.118.251801. Epub 2017 Jun 19.
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_{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 σ[over ¯]{f} of (5.90±0.13)×10^{-43} cm^{2}/fission and a fuel-dependent variation in the IBD yield, dσ{f}/dF_{239}, of (-1.86±0.18)×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 is 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 3.1σ. This discrepancy indicates that an overall deficit in the 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±0.17) and (4.27±0.26)×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 yields suggests that this isotope may be the primary contributor to the reactor antineutrino anomaly.
大亚湾实验观测到反应堆堆芯燃料演变与反应堆反中微子通量及能谱变化之间的相关性。在两个实验大厅中的四个反中微子探测器，用于在大亚湾核电站和岭澳核电站的六个2.9吉瓦热功率反应堆堆芯的多个燃料循环期间，历时1230天识别出220万个逆β衰变（IBD）。利用有效²³⁹Pu裂变份额F₂₃₉从0.25至0.35的探测器数据，大亚湾测量出平均IBD产额σ[上划线]ₓ为(5.90±0.13)×10⁻⁴³平方厘米/裂变，以及IBD产额中与燃料相关的变化量dσₓ/dF₂₃₉为(-1.86±0.18)×10⁻⁴³平方厘米/裂变。这一观测在10个标准差水平上否定了反中微子通量随²³⁹Pu裂变份额保持恒定的假设。发现IBD产额的变化与能量相关，在5.1个标准差水平上否定了反中微子能谱保持恒定的假设。虽然IBD能谱演变的测量结果与近期反应堆模型的预测总体一致，但测量得到的总IBD产额演变与近期预测在3.1σ水平上存在分歧。这种差异表明，测量通量相对于预测的总体不足并非源于主要裂变同位素²³⁵U、²³⁹Pu、²³⁸U和²⁴¹Pu同等程度的分数不足。基于测量到的IBD产额变化，已确定两种主要裂变母体同位素²³⁵U和²³⁹Pu的产额分别为(6.17±0.17)和(4.27±0.26)×10⁻⁴³平方厘米/裂变。观测到的²³⁵U产额与预测产额之间7.8%的差异表明，该同位素可能是反应堆反中微子异常的主要贡献者。
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