| Project/Area Number |
18540299
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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 |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | High Energy Accelerator Research Organization |
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Principal Investigator |
ISHIHARA Nobuhiro High Energy Accelerator Research Organization, Institute of Particle and Nuclear Studies, Professor (50044780)
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| Co-Investigator(Kenkyū-buntansha) |
OHMA Taro High Energy Accelerator Research Organization (KEK), Institute of Particle and Nuclear Studies, Researcher (60100814)
KITAMURA Shoichi Tokyo Metropolitan University, Faculty of Health Sciences, Professor (60106599)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,560,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2007: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2006: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Keywords | Double beta decay / Majorana neutrino / Neutrino mass / マヨラナ粒子 |
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| Research Abstract |
Double beta decay is the phenomenon that the nucleus in an atom emits two beta rays and increases its atomic number by two units. In this case, 2vββ means the emission of two anti-electron-neutrinos together with two beta rays, and 0vββ stands for no neutrino emission therefore it is called the neutrinoless double beta decay. So far 2vββ's of several atoms have been observed and their halflives have been measured, while no observation of Ovββ has been confirmed yet. If neutrinos are Majorana particles, Ovββ should take place. In other words, the observation of Ovββ means that neutrinos are Majorana particles, and the measurement of its haifiife can determine the absolute mass scale of neutrinos. This contributes to constructing the new theory of elementary particles beyond the old standard modeL And also, the observation of Ovf3f3 will support the leptogenesis theory, which is considered as the strong candidate of early universe scenario. The DCBA (Drift Chamber Beta-ray Analyzer) experiment measures the momentum of each beta ray in a uniform magnetic field by drift chamber tracking detectors. This is the unique method not realized elsewhere so far. The DCBA chamber is only sensitive to charged particles therefore it can intrinsically eliminate gamma ray backgrounds. Particle identification among electron, positron and alpha particle is easy because of the magnetic field, and it is very powerful for rejecting charged particle backgrounds. These have been confirmed using the prototype called DCBA-T2 in the present research. DCBA-T2 has revealed the method to improve the energy resolution, which is the key issue of separating Ovββ events from 2vββ events. Then new prototype DCBA-T3 is now under construction based on the experiences of DCBA-T2. In the future, an enlarged detector module is planed in order to search for Ovββ events with a large amount of decay sources.
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