| Project/Area Number |
17K05479
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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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 |
Komatsubara Takeshi 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 教授 (30242168)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2018: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2017: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
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| Keywords | K中間子 / 崩壊 / 稀崩壊 / 新粒子探索 / フレーバー物理 / ダーク / 素粒子実験 / 加速器 / 大強度陽子ビーム |
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| Outline of Final Research Achievements |
We search for neutral and light new-particles X0 that appear through a two-body decay of long-lived neutral K meson, KL→π0X0, in the KOTO experiment at the Hadron Experimental Facility of Japan Proton Accelerator Research Complex, J-PARC. Based on the analysis of the data taken in 2015, new results on the KL→π0X0 decay were obtained and published. From the anaysis of the data taken in 2016-2018, we observed four candidate events in the signal region. Currently we are doing further checks on the four events and careful examinations on their origin.
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| Academic Significance and Societal Importance of the Research Achievements |
平成27年のデータをもとに得られたKL→π0X0崩壊の分岐比に対する上限値、X0の質量が135MeVの場合に90%の信頼水準で 4.2億回に一度、はこの崩壊に対する世界で最も低く厳しい値です。平成28-30年のデータで観測された四つの候補事象は、現在の分岐比の感度ではKL→π0νν崩壊ではなくKL→π0X0崩壊と解釈するのが自然です。いずれも、学術的意義が高く、自然法則の深い理解へさらに歩を進める結果です。
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