1996 Fiscal Year Final Research Report Summary
Study of High Energy Neutrino by Deep Ocean Detector
| Project/Area Number |
08044058
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | The University of Tokyo |
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Principal Investigator |
OHASHI Yozo Univ. of Tokyo. ICRR. Assoc. Prof., 宇宙線研究所, 助教授 (80022599)
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| Co-Investigator(Kenkyū-buntansha) |
HAYASHINO Tomoki Tohoku Univ., Phys. Dep. Assis. Prof., 理学部, 助手 (10167596)
YAMAGUCHI Akira Tohoku Univ., Phys. Dep. Prof., 理学部, 教授 (60004470)
OKADA Atsushi Univ. of Tokyo. ICRR. Assis. Prof., 宇宙線研究所, 助手 (90013341)
UEHARA Sadaharu KEK. Sec. Syst. Phys., Assis. Prof., 物理第二研究系, 助手 (70176626)
KOBAYAKAWA Keizo Fukui Inst. Tech., Liveral arts. Prof., 教養部, 教授 (00031287)
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| Project Period (FY) |
1996
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| Keywords | cosmic neutrino / deep underwater / optical detector |
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| Research Abstract |
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1). Highly Sensitive Optical Detector for a use in Deep Underwater ;
The optical detector is one of the most important components of the water Cerenkov apparatus in the deep ocean. The detector is required to be sensitive to low level signal as one-photon and to have rating pressure more than 500 atm. The optical sensor is a 15" photomultiprier, which is contained in the 17" glass housing3 72 optical detectors enough to construct 3-strings were fabricated and its sensitivity was calibrated using a laser light source and Cerenkov light radiated by a cosmic-ray. Once 1-string composed of 24 optical detectors was deployed on the deep ocean floor, and the detector was proved to function as designed. Some defects were found on the limited number of glass housing at the processed part for connector.
2). A Search for High Energy Neutrinos from Active Galctic Nuclei ;
In the deep ocean the light attenuation length is as large as 40m, and at extremely high energy neutrino interaction produces nuclear or electromagnetic cascade, which emits strong light. As the results the effective volume of the deep ocean Cerenkov detedtor bocomes quite large than the size of the detector itself. In 1987 a prototype experiment using 7-optical detectors was performed at great depth from 2000m to 4000m. The optical detectors were mounted along a string at 0.2m interval and it was found the effective mass of the detector was as large as 10ィイD16ィエD1 tons at neutrino energy above 10ィイD16ィエD1 GeV. Due to different path lengths a cascade signal can be discriminated from a muon signal. The data from 10.6 hours observation with 7-optical detectors was reanalyzed and the neutrino flux from cosmic origin was examined at neutrino energy E*≧ 100 TeV.
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