| Co-Investigator(Kenkyū-buntansha) |
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)
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)
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| Research Abstract |
We ran KTeV experiment in 1996-1997, and have obtained the following results.
* We have established the existance of direct CP violation, CP violation in the decay itself, instead of in the K^0-K^0 mixing. This is based on the result that the double ratio between the four branching ratios of K_L, S→π^+π^-, π^0π^0 decays is deviated from unity by 7 standard deviations. Based on this result and the result by CERN experiments, Super Weak model was rejected as the sole source of CP violation.
* We have observed the CP violation in the distribution of angle between ee and ππ planes in the K_L→ππee decays. This is the first time that the CP violation was found in the kinematical distributions.
* New upper limits on the branching ratios were set for the CP violating rare decays, K_L→π^0ee, K_L→π^0μμ, and K_L→π^0vv.
* In addition, we have measured branching ratios and form factors for other rare K decays and hyperon decays.
In 1999-2000, we had the second run, and collected the same amount of data for K_<L,S>→ππ events, and 2-3 times the data for rare decays.
We are currently designing a new experiment to measure the CP violation parameter by using K_L→π^0vv decays. For this experiment, we measured the kaon and neutron flux and energy distributions by bombarding the target by 150GeV protons.
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