Study of CP Violation in the Neutral Kaon System
| Project/Area Number |
09044083
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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 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, Osaka University, Associate Professor, 大学院・理学研究科, 助教授 (20243157)
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| Co-Investigator(Kenkyū-buntansha) |
SADAMOTO Masayoshi Graduate School of Science, JSPSFellow, 大学院・理学研究科, 日本学術振興会特別研
HARA Takanori Graduate School of Science, Osaka University, Assistant, 大学院・理学研究科, 助手 (70283827)
HAZUMI Masashi Graduate School of Science, Osaka University, Assistant, 大学院・理学研究科, 助手 (20263197)
TAKITA Masato Graduate School of Science, Osaka University, Assistant, 大学院・理学研究科, 助手 (20202161)
NAGASHIMA Yorikiyo Graduate School of Science, Osaka University Professor, 大学院・理学研究科, 教授 (90044768)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥4,600,000 (Direct Cost: ¥4,600,000)
Fiscal Year 1998: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1997: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | CP Violation / Neutral Kaon / Weak interaction / Rare decays |
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| Research Abstract |
We ran KTeV Experiment at Fermilab from 1996 to 1997, and obtained following results.
1. We found that the CP is violated in the decay itself (direct CP violation), by measuring the double ratio of the branching fractions of K_L, Ks * <product> + <product> -and <product>^0 <product>^0 decays. Based on the 20% of the data, we obtained a preliminary result, Re(e'/e) * (28 0*4.1) x 10^<-4> which is more than 6 standard deviations away from 0. This result rejects the Superweak model which was one of the theories explaining the CP violation mechanism.
2. We observed the first CP violation in a kinematical variable, the asymmetry in the distribution of the angle between <product> + <product>- and e+e-planes, in the K_L * <product> + <product> e+e- decay.
3. We searched for the decay K_L * <product>^Onunu, which is dominated by direct CP violation, and set the best upper limit on the branching ratio, <5.9x10^7 (90%CL) (preliminary).
We also measured the detection inefficiency of photon detectors due to photo-nuclear interactions by using tagged photon beam at KEK Tanashi. We found that pure CsI and lead/scintillator sandwich detectors satisfy the specs necessary for the future K_<1L> * _<1@ : S1O>nunu experiments.
We had an international workshop on the CP violation in K, and had an extensive discussion on the future experiments to measure the branching ratio of K_L * ^Onunu decay.
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Report
(3 results)
Research Products
(9 results)
