1987 Fiscal Year Final Research Report Summary
Precise Measurement of The Electron Anti-Neutrino Mass
| Project/Area Number |
60420006
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | University of Tokyo |
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Principal Investigator |
OHSHIMA Takayoshi Institute for Nuclear Study, University of Tokyo, 原子核研究所, 助手 (00134651)
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| Co-Investigator(Kenkyū-buntansha) |
NAOTAKE Morikawa Isotope Centre, University of Tokyo, アイソトープ総合センター, 教授 (70011525)
YASUTAKA Fukushima National Labratory for High Energy Physics, KEK, 助教授 (10150004)
KUMATARO Ukai Institute for Nuclear Study, University of Tokyo, 原子核研究所, 助教授 (40013411)
HIROKANE Kawakami Institute for Nuclear Study, University of Tokyo, 原子核研究所, 助手 (50013412)
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| Project Period (FY) |
1985 – 1987
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| Keywords | Neutrino / Mass / Beta-decay / Tritium / LB-film / Cadmium / オージェ電子 |
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| Research Abstract |
1. The upper limit for the neutrino mass was obtained from the measured ^3H <beta> -spectrum as : m_<<nu>> < 32eV (90%CL) in 1986, m_<<nu>> < 28eV (90%CL) in 1987. 2. Particular points of our experiment, realized by this Grant-in Aid, are : (1) The world highest energy resolution of <DELTA>E/E = 4x10^<-4> is achieved.
(2) Technique for preparing the large sized thin ^3H and ^<109>Cd films as sources was established by means of the Langmuir-Blodgett (LB) method.
(3) The response of the spectrometer can be reliably and experimentally determined with ^<109>Cd source, which has the same chemical composition with ^3H source.
3. To improve the mass sensitivity, (1) New technique is established to prepare 5 times larger LB film (60x200mm^<>) than the former. (2) New position sensitive <beta>-ray detector, which improves the count rate by a factor of 6, is built. With these developements in 1987, the count rate and S/N ratio will be enhanced by a factor of 30 than the former measurements, and the upper limit of <wave>10eV will be reached at the coming experiment.
4. ^<109>Ag KLL Auger lines employed to deduce the response function, and also KLM and KLN lines were measured. Resultant line energies and transition probabilities are the most accurate data so far for the medium Z atoms.
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