MEASUREMENT OF CP VIOLATION PARAMETER USING RARE KAON DECAYS

衰变KL→π^&lt；0&gt；νν是测量CP破坏参数的最佳衰减器之一，我们准备了实验KEK E391a来寻找灵敏度最高的衰减器，并于2004年2月开始运行。该实验也将作为下一步实验测量其分支比的先导实验。我们利用蒙特卡罗模拟对J-PARC 50GeV质子加速器的一个新实验进行了研究。我们发现，通过利用衰变区的一侧作为量热计，接受度增加了4倍。在加速器设计强度为10%的情况下，我们可以观测150个信号事件，测量CP破坏参数的精度为6%。我们还研制了一种可以测量光子入射角的新型热量计。这是一种Shashlik类型的探测器，带有单独的光纤读取3个不同深度区域中的一个。用1.5-2.8GeV光子在SPRIN8上进行的测试实验表明，它的角分辨率为9%/平方英尺(E(GeV))。通过提高光产额等方法可以进一步提高分辨率。我们还开发了一种新型的光导，可以将来自光纤的光以浅入射角度注入光管。我们还公布了费米实验室KTeV实验的结果，包括CP破坏参数ε‘/ε的测量，建立了直接的CP破坏。

The decay KL→π^<0>νν is one of the best decays to measure the CP violation parameter.We prepared experiment KEK E391a to search for the decay with the best sensitivity, and started running in February 2004. The experiment will also serve as a pilot experiment for the next experiment to measure its branching ratio.We studied a new experiment for J-PARC 50GeV proton accelerator using Monte Carlo simulation. We found that the acceptance is increased by a factor 4 by utilizing the side of the decay region as a calorimeter. With the 10% of the design intensity of the accelerator, we can observe 150 signal events and measure the CP violation parameter with a 6% accuracy.We also developed a new calorimeter which can measure the incident angle of photons. This is a shashlik type detector with individual fibers reading one of the 3 different depth regions. A test experiment using 1.5-2.8GeV photons at SPring8 showed that it has an angle resolution of 9%/ Sqrt (E (GeV) ). The resolution can be improved further by increasing the light yield etc..We also developed a new type of light guide to inject the light from fibers to a phototube at a shallow incident angle. Using the light guide, the number of photoelectrons was increased by a factor 1.8.We also published results from Fermilab KTeV experiment, including the measurement of CP violation parameter, ε'/ε, establishing the direct CP violation.