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Precise measurement of the zenith-angle distribution of atomospheric neurtrinos and a study of neutrino oscillations

大气中微子天顶角分布的精确测量及中微子振荡研究

基本信息

批准号：
09440101
负责人：
KAJITA Takaaki
金额：
$ 9.34万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09440101/
关键词：
atmospheric neutrino neutrino neutrino oscillation mu-neutrino tau-neutrino 天頂角

项目摘要

We studied neutrino oscillations using the atmospheric neutrino data from Super Kamiokande.Multi-GeV muon-like data showed a significant deficit of the upward-going events. Up/down ratio of these events was 0.56 ± 0.04(statistical) ± 0.01(systematic) and deviated from the expectation (unity) in the absence of neutrino oscillations by more than 8 standard deviations. The data can be naturally explained by neutrino oscillations, since the neutrinos change their flavor by neutrino oscillations after traveling long distances. This conclusion was supported by the muon/electron ratio of the neutrino events and by detailed studies of the upward-going muon events. We conclude that the atmospheric neutrino data from Super-Kamiokande give evidence for neutrino oscillations.The atmospheric neutrino data are explained by the neutrino oscillations between muon-neutrinos and tau-neutrinos. However, it is possible to explain the data by introducing neutrino oscillations between muon-neutrinos and non-interacting sterile-neutrinos. We have carefully studied this possibility and found that the oscillations to sterile neutrinos are disfavored at about 99% C.L.In summary, we conclude that neutrino oscillations are between muon-neutrinos and tau-neutrinos. The difference of the neutrino mass squared is between 2 〜 5 × 10ィイD13ィエD1eVィイD12ィエD1, and the mixing angle between the two neutrinos is sin22 θ > 0.88, at 90% C.L.

我们利用超级神冈的大气中微子数据研究了中微子振荡，多GeV的类μ子数据显示了上升事件的显著亏损。这些事件的上升/下降比为0.56 ± 0.04（统计）± 0.01（系统），偏离预期（单位）在没有中微子振荡超过8个标准差。这些数据可以很自然地用中微子振荡来解释，因为中微子在长距离旅行后会通过中微子振荡改变它们的味道。中微子事件的μ子/电子比和对上行μ子事件的详细研究支持了这一结论。我们认为Super-Kamiokande的大气中微子数据提供了中微子振荡的证据，大气中微子数据可以用μ中微子和τ中微子之间的中微子振荡来解释。然而，可以通过引入μ中微子和无相互作用的不育中微子之间的中微子振荡来解释这些数据。我们仔细研究了这种可能性，发现在99%C. L附近，对不育中微子的振荡是不利的。总之，我们得出中微子振荡介于μ中微子和τ中微子之间的结论。在90%C. L时，中微子质量的平方差在2 × 10 ~（-5）× 10 ~（-1）D ~（13）V ~（-1）D ~（12）V ~（-1）D ~（-1）之间，两个中微子的混合角为sin ~（22）θ > 0.88。