Measurement of CP violation parameter phi-2

B厂加速器KEKB是世界上光度最高的机器，在2003年5月达到了设计光度10^&lt；34&>cm；-2&gt；S^&lt；-1&gt；，并且还在不断刷新光度纪录。2003年夏天，贝尔实验对硅顶点探测器进行了升级，并积累了良好的数据。对于课题PHI-2测量，我们分析并公布了基于积分光度253fb-14数据的π+π衰变模式的结果。参数A和S如下所示。A=+0.56±0.12(统计)±0.06(系统)，S=-0.67±0.16(统计)±0.06(系统)。因此，继2001年在J/ΨK衰变模式中发现CP破坏之后，我们也证实了该通道中CP破坏的存在。这一结果也有力地表明，在B介子衰变中第一次出现了直接的CP破坏，因为A是非零且超过4西格玛意义的。我们还利用同位旋关系限制了phi2的箭头范围。这一结果有力地支持了标准模型中小林-马斯卡瓦机制的框架，与其他间接测定结果一致。我们还考察了A1π衰变模式，目的是为了增加测量phi2角的统计量，并首次确定了这种决定分支分数的衰变模式的存在。作为对Belle实验的另一项贡献，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，我们还在分析工具的开发方面做出了贡献：一种是在区分B介子和反B介子方面具有很高的标记效率，一种是抑制连续介质事件的贡献等。在硬件方面，我们开发了新安装的硅顶点探测器(SVD-2)的触发系统，为SVD-2的性能改进做出了很大贡献。

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.