| Project/Area Number |
11440079
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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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 | Osaka University |
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Principal Investigator |
YAMANAKA Taku Graduate School of Science, Associate Professor, 大学院・理学研究科, 助教授 (20243157)
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| Co-Investigator(Kenkyū-buntansha) |
HARA Takanori Graduate School of Science, Assistant, 大学院・理学研究科, 助手 (70283827)
HAZUMI Masashi Graduate School of Science, Assistant, 大学院・理学研究科, 助手 (20263197)
NAGASHIMA Yorikiyo Graduate School of Science, Professor, 大学院・理学研究科, 教授 (90044768)
INAGAKI Takao High Energy Accelerator Research Organization, Institute of Particle and Nuclear Studies, Professor, 素粒子原子核研究所, 教授 (60044757)
瀧田 正人 大阪大学, 大学院・理学研究科, 助手 (20202161)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥9,100,000 (Direct Cost: ¥9,100,000)
Fiscal Year 2000: ¥5,300,000 (Direct Cost: ¥5,300,000)
Fiscal Year 1999: ¥3,800,000 (Direct Cost: ¥3,800,000)
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| Keywords | CP violation / photon detector / neutral kaons / rare decays |
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| Research Abstract |
We are planning a new experiment to measure the CP violating parameter in the standard model, η, by measuring the branching ratio of K_L→π^0vv^^-. The major background to this decay is K_L→π^0π^0 where we miss 2 out of 4 photons. In order to suppress this background, we will cover the decay region by a hermetic photon veto counters made of lead/scintillator sandwich.
Here is a summary of what we have done.
1. We found that the detection inefficiency of lead/scintillator sandwich would be smaller if the layers were aligned at angle (60 degrees) instead of aligning them in parallel (0 degrees) to the beam line. Also, the detection efficiency increases if the scintillator layers are extended to cover
the surface of exposed lead sheets.
2. We are planning to read out the light from scintillator planes by using optical fibers with a wave length shifter, embeded in grooves. We studied the position dependence of the scintillator light collected in the fiber. We found that the light output is determined by the solid angle of the fiber, reflection/diffusion at the grooves, and the light loss at the surface reflections. The measured results were reproduced by simple model calculations.
3. We have optimized cuts for the experiment to keep a high sensitivity while suppressing background events from K_L→π^0π^0.
4. We have measured the flux and the energy spectrum of kaons and neutrons produced by 150GeV proton beam.
5. Based on above studies, we are now preparing a proposal for the new experiment to be submitted in April.
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