Study of atmospheric neutrinos

大气中微子研究

• 批准号: 07640380
• 负责人: KAJITA Takaaki
• 金额: $ 1.41万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640380/
• 关键词: neutrino; atmospheric neutrino; neutrino oscillation; ミューニュートリノ; 電子ニュートリノ

Atmospheric neutrinos arise from the decay of pions (and kaons) produced by primary cosmic-ray interactions in the atmosphere. It is expected that the flux ratio between muon neutrinos and electron neutrinos is about 2. However, the experimental result from Kamiokande on this ratio was about 1.2. This observation, if confirmed, could be evidence for neutrino oscillations and is potentially very important.In this research project, we carried out a detailed flux calculation, a study of neutron background in the atmospheric neutrino sample and an analysis of upward-going muons which were produced by high energy atmospheric muon neutrinos. We found that the contamination of neutron background in the electron-like sample was less than 1%. The analysis of the upward-going muons suggested that the upward-going muon data were consistent with the fully contained atmospheric neutrino events if the neutrino oscillation effects were taken into account. From these studies, we concluded that the present data could be evidence for neutrino oscillations. Both the numu*nue and numu*nutau oscillation channels could explain the present data.

大气中微子是由大气中初级宇宙射线相互作用产生的介子（和介子）衰变产生的。预计μ子中微子与电子中微子的通量比约为2。然而，Kamiokande的实验结果约为1.2。这一观察结果如果得到证实，可能成为中微子振荡的证据，并且可能非常重要。在这个研究项目中，我们进行了详细的通量计算，研究了大气中微子样本中的中子背景，并对高能大气μ子中微子产生的上行μ子进行了分析。我们发现类电子样品中中子背景污染小于1%。对上行μ子的分析表明，如果考虑中微子振荡效应，则上行μ子数据与完全包含的大气中微子事件一致。从这些研究中，我们得出的结论是，目前的数据可能是中微子振荡的证据。 numu*nue 和 numu*nutau 振荡通道都可以解释当前数据。

项目成果

S.Kasuga et al.: "A study of the e/μ identification capability of a water Cerenkov detector and the atmospheric neutrino problem" Physics Letters B. 374. 238-242 (1996)

S. Kasuga 等人：“水切伦科夫探测器的 e/μ 识别能力和大气中微子问题的研究”《物理快报》B. 374. 238-242 (1996)

M.Honda et al.: "Calculation of the flux of atmospheric neutrinos" Physical Review D. 52. 4985-5005 (1995)

M.Honda 等人：“大气中微子通量的计算”物理评论 D. 52. 4985-5005 (1995)

Y.Fukuda et al.: "Study of neutron background in the atmospheric neutrino sample in kamiokande" 388. 397-401 (1996)

Y.Fukuda 等：“kamiokande 大气中微子样本中的中子背景研究”388. 397-401 (1996)

S.Kasuga et al.: "A study of the e/μ identification capabilities of a water Cerenkov detector and the atmospheric neutrino problem" Physics Letters B. (発表予定). (1996)

S. Kasuga 等人：“水切伦科夫探测器的 e/μ 识别能力和大气中微子问题的研究”Physics Letters B.（待出版）。