Study of CP Violation in the Neutral Kaon System

本项目的目的是从两个方面研究中性K介子系统中的CP破坏。一个是高精度地测量K_L、K_S* pi ^0 pi ^0和pi^+pi^-分支比的双比（KTeV E832）。这个比值偏离1是弱衰变本身CP破坏的证明（直接CP破坏）。另一个是寻找以CP直接破坏效应为主的稀有K_L衰变（KTeV E799），我们在美国费米国家加速器实验室准备了新的实验。特别是我们负责CsI电磁量能器的光电管、快速数据采集系统和专用的光子否决计数器。实验于1995年8月底接收了第一束中性束，并证实该束是干净的。我们于1996年对E832进行了2个月的数据采集，并从1月中旬开始对E799进行数据采集。1997.经过几次转换，我们计划将数据保存到1997年9月。我们预期在1997年年底的某个时候开始有初步的结果。我们还为B工厂的实验开发了新的硅条探测器。经过计算机模拟优化，测试系统的开发，以及对各种原型的测试，我们已经确定了最终的设计。很快就会开始大规模生产。

The purpose of this project is to study the CP violation in the neutral kaon system from two fronts. One is to measure the double ratio of branching ratios of K_L, K_S*pi^0pi^0, and pi^+pi^- with a high precision (KTeV E832). The deviation of this ratio from unity is a proof of CP violation in the weak decay itself (direct CP violation). The other is to search for rare K_L decays where the effect of direct CP violation is dominant (KTeV E799).We have prepared the new experiments at Fermi National Accelerator Laboratory at U.S.A.. In particular, we were reponsible for the phototubes for the CsI electromagnetic calorimeter, fast data acquisition system, and a special photon veto counter.The experiment received the first neutral beam at the end of August 1995, and it was confirmed that the beam was clean as designed.We took data for E832 for 2 months in 1996, and started taking data for E799 from mid-January, 1997. With a couple of switchovers, we plan to take data till September, 1997. We expect to start having preliminary results sometime late 1997.We have also developed new silicon strip detectors for the B-factory experiment. After optimization with computer simulation, development of test system, and testing various prototypes, we have decided the final design. The mass production will start soon.