Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
Univ. Grenoble Alpes, Université Savoie Mont Blanc, CNRS/IN2P3, LAPP, 74000 Annecy, France.
Phys Rev Lett. 2018 Oct 19;121(16):161801. doi: 10.1103/PhysRevLett.121.161801.
The reactor antineutrino anomaly might be explained by the oscillation of reactor antineutrinos toward a sterile neutrino of eV mass. In order to explore this hypothesis, the STEREO experiment measures the antineutrino energy spectrum in six different detector cells covering baselines between 9 and 11 m from the compact core of the ILL research reactor. In this Letter, results from 66 days of reactor turned on and 138 days of reactor turned off are reported. A novel method to extract the antineutrino rates has been developed based on the distribution of the pulse shape discrimination parameter. The test of a new oscillation toward a sterile neutrino is performed by comparing ratios of cells, independent of absolute normalization and of the prediction of the reactor spectrum. The results are found to be compatible with the null oscillation hypothesis and the best fit of the reactor antineutrino anomaly is excluded at 97.5% C.L.
反应堆反中微子反常现象可能可以用反应堆反中微子向质量为 eV 的惰性中微子的振荡来解释。为了探索这一假设，STEREO 实验在距离 ILL 研究堆紧凑核心 9 到 11 米的六个不同探测器单元中测量反中微子能谱。在本 Letter 中，报告了反应堆开启 66 天和关闭 138 天的结果。已经开发了一种新的方法，基于脉冲形状鉴别参数的分布来提取反中微子的速率。通过比较独立于绝对归一化和反应堆谱预测的单元比值，对朝向惰性中微子的新振荡进行了测试。结果与零振荡假设相容，在 97.5%置信水平下排除了反应堆反中微子反常的最佳拟合。
