1996 Fiscal Year Final Research Report Summary
Study of atmospheric neutrinos
| Project/Area Number |
07640380
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | University of Tokyo |
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Principal Investigator |
KAJITA Takaaki University of Tokyo, Institute for Cosmic Ray Research, Associate Professor, 宇宙線研究所, 助教授 (40185773)
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| Co-Investigator(Kenkyū-buntansha) |
TAKITA Masato Osaka University, Department Physics, Research Assistant, 理学部, 助手 (20202161)
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| Project Period (FY) |
1995 – 1996
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| Keywords | neutrino / atmospheric neutrino / neutrino oscillation |
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| Research Abstract |
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.
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