Study of CP Violation in Neutral Kaon System

中性Kaon体系中CP破坏的研究

基本信息

批准号：
11694078
负责人：
YAMANAKA Taku
金额：
$ 2.88万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11694078/
关键词：
CP Violation Weak interaction Rare K decays 中性K中間子稀崩壊 CP非保存 K中間子

项目摘要

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.

我们在1996-1997年进行了KTeV实验，并得到了以下结果。*我们已经确定了直接CP破坏的存在，CP破坏存在于衰变本身，而不是在K^0-K^0混合中。这是基于的。基于此结果，K_L、S→π^+π^-、π^0π^0 的四个分支比之间的双倍比率衰减偏离统一 7 个标准差。 CERN 实验的结果，超弱模型被拒绝作为 CP 破坏的唯一来源。*我们在 K_L→ππee 中观察到 ee 和 ππ 平面之间的角度分布存在 CP 破坏，这是第一次出现 CP 破坏。在运动学分布中发现了 CP 违规。*为 CP 违规罕见衰变设置了新的分支比上限，K_L→π^0ee，K_L→π^0μμ，和K_L→π^0vv。*此外，我们还测量了其他罕见的K衰变和超子衰变的分支比和形状因子。在1999-2000年，我们进行了第二次运行，并收集了相同数量的K_<L数据，S>→ππ 事件，以及罕见衰变数据的 2-3 倍。我们目前正在设计一个新的实验，通过使用 K_L→π^0vv 衰变来测量 CP 破坏参数。实验中，我们通过150GeV质子轰击目标来测量Kaon和中子通量以及能量分布。