Title: Search for an eV-scale sterile neutrino with the first six detection units of KM3NeT/ORCA Show Chinese title

Title: 以KM3NeT/ORCA的前六个探测单元搜索eV量级的惰性中微子

Abstract: The existence of an eV-scale sterile neutrino has been proposed to explain several anomalous experimental results obtained over the course of the past 25 years. The first search for such a sterile neutrino conducted with data from KM3NeT/ORCA -- a water Cherenkov neutrino telescope under construction at the bottom of the Mediterranean Sea -- is reported in this paper. GeV-scale atmospheric neutrino oscillations are measured by reconstructing the energy and arrival direction of up-going neutrinos that have traversed the Earth. This study is based on a data sample containing 5828 neutrino candidates collected with 6 detection units ($5\%$ of the complete detector), corresponding to an exposure of 433 kton-years. From the expected effect of an eV-scale sterile neutrino on the first $\nu_\mu \rightarrow \nu_\tau$ standard oscillation maximum, simultaneous constraints are put on the magnitude of the $U_{\mu 4}$ and $U_{\tau 4}$ mixing elements under the assumption $\Delta m^2_{41} = 1$ eV$^2$. The results are compatible with the absence of mixing between active neutrinos and a sterile state, with $|U_{\mu 4}|^2 < 0.138$ and $|U_{\tau 4}|^2 < 0.076$ at a $90\%$ confidence level. Such constraints are compatible with the results reported by other long-baseline experiments, and indicate that with KM3NeT/ORCA it is possible to bring crucial contributions to sterile neutrino searches in the coming years. Show Chinese abstract

Abstract: 一个eV量级的惰性中微子的存在已被提出，以解释过去25年间获得的若干异常实验结果。 本文报告了利用KM3NeT/ORCA——位于地中海底部正在建设中的水切连科夫中微子望远镜——的数据进行的首次此类惰性中微子搜索。 通过重建穿过地球的上行中微子的能量和到达方向，测量了GeV量级的大气中微子振荡。 本研究基于包含5828个中微子候选事例的数据样本，这些事例是使用6个探测单元（$5\%$的完整探测器）收集的，对应于433千吨年暴露量。 在假设$\Delta m^2_{41} = 1$ eV$^2$的前提下，从eV量级惰性中微子对第一个$\nu_\mu \rightarrow \nu_\tau$标准振荡最大值的预期影响出发，同时对$U_{\mu 4}$和$U_{\tau 4}$混合元素的大小进行了限制。 结果与活性中微子和一个惰性态之间不存在混合相容，在$|U_{\mu 4}|^2 < 0.138$和$|U_{\tau 4}|^2 < 0.076$的置信度为$90\%$。 这些限制与其他长基线实验报告的结果相容，并表明在未来几年内，通过 KM3NeT/ORCA 可以对惰性中微子搜索做出重要贡献。