Measurement of CP violation parameter phi-2

B厂加速器KEKB是世界上亮度最高的机器，在2003年5月达到了设计亮度10^<34>cm^<-2>s^<-1>，并且还在不断提高其亮度记录。Belle实验于2003年夏季对硅顶点探测器进行了升级，并在良好的状态下积累了数据。在研究课题phi-2测量方面，我们分析并发表了基于集成光度253fb-14数据的π+ π-衰变模式的结果，该数据比之前的出版物大4倍。其中参数A、S的计算公式如下。= + 0.56±0.12 (stat)±0.06(系统),S = -0.67±0.16 (stat)±0.06(系统)。因此，继2001年在J/ΨK衰变模式中发现CP违和之后，我们也证实了该通道中CP违和的存在。这一结果也首次有力地表明在B介子衰变中存在直接CP违逆，因为A是非零的显著性超过4 σ。我们还利用同位旋关系限制了phi2的箭头范围。该结果有力地支持了标准模型中Kobayashi-Maskawa机制的框架，与其他间接判定一致。为了提高测量π角的统计量，我们还研究了π衰减模式，并首次建立了这种决定分支分数的衰减模式的存在。作为对Belle实验的其他贡献，我们使用购买的计算机场生成了大量的蒙特卡罗模拟数据。此外，他还在开发分析工具方面做出了贡献：一个在区分B介子和反B介子方面提供了高标记效率，一个抑制了连续体事件的贡献，等等。在硬件方面，我们为新安装的硅顶点探测器（SVD-2）开发了触发系统，并在提高SVD-2的性能方面做出了很大贡献。

The B factory accelerator KEKB is the world highest luminosity machine, achieving the design luminosity of 10^<34>cm^<-2>s^<-1> in May 2003, and still improving is luminosity record. The Belle experiment has upgraded the silicon vertex detector in summer 2003, and accumulates data in a good condition.About the research topic phi-2 measurement, we have analyzed and published the results on the π+ π- decay mode based on the data of integrated luminosity 253fb-14 four times larger than that of the previous publication. The parameter A and S are obtained as follows. A=+0.56±0.12(stat.)±0.06(syst.), S=-0.67±0.16(stat.)±0.06(syst.). Thus, we have established the existence of CP violation in this channel, too, following the discovery of CP violation in the J/ΨK decay mode in 2001. This result also strongly indicates that there is direct CP violation for the first time in B meson decay, because A is nonzero by more than 4 sigma significance. We also limit the arrowed range of phi2 by using the isospin relations. The result strongly supports the framework of the Kobayashi-Maskawa mechanism in the standard model, agreeing with other indirect determination.We have also looked at a1πdecay modes toward the aim of increasing the statistics in measuring the angle phi2 and established the existence of this decay mode determining the branching fraction for the first time. As the other contributions to the Belle experiment, we generated large amount of Monte Carlo simulation data using the purchased computer farm. Furthermore e also contributed in developing analysis tools : one gives high tagging efficiency in distinguishing the B meson from the anti-B meson, one to suppress the contribution of continuum events, etc. On the hardware side, we have developed the trigger system for the newly installed silicon vertex detector (SVD-2) and contributed much in improving the performance of the SVD-2.