Measurement of CP violation parameter phi-2

CP违规参数phi-2的测量

• 批准号: 13440074
• 负责人: WATANABE Yasushi
• 金额: $ 8.45万
• 依托单位: Tokyo Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13440074/
• 关键词: Symmetry btw matter and antimatter (2) B factory; CP Violation; Kobayashi-Maskawa Mechanism; Standard Model in particle Physics; Experiment with accelerator; B meson; Asymmetric energy collider; 非対称工ネルギー加速器; 物質・反物質間の対称性の破れ; 標準理論; カビボ・小林・益川行列; B

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.

B工厂加速器KEKB是世界上亮度最高的加速器，于2003年5月达到了10^<34>cm^<-2>s^<-1>的设计亮度，并且仍在不断提高亮度记录。贝儿实验在2003年夏季对硅顶探测器进行了升级改造，积累了较好的数据，在phi-2测量的研究课题上，我们分析并发表了基于积分光度253 fb-14的π+ π-衰变模式的结果，该数据比以前的文献大4倍。参数A和S如下获得。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/K衰变模式中发现CP破坏之后，我们也建立了该通道中CP破坏的存在。这一结果也有力地表明，在B介子衰变中首次存在直接的CP破坏，因为A的非零性大于4 σ。我们还利用同位旋关系限制了φ 2的箭头范围。这一结果有力地支持了标准模型中Kobayashi-Maskawa机制的框架，与其他间接测定结果一致。我们还研究了α 1 π衰变模式，目的是增加测量角φ 2的统计量，并首次建立了这种衰变模式决定分支分数的存在。作为对贝儿实验的另一贡献，我们利用购买的计算机农场生成了大量的蒙特卡罗模拟数据。此外，e也有助于开发分析工具：一个给出了高的标签效率区分B介子从反B介子，一个抑制连续事件的贡献等在硬件方面，我们已经开发了新安装的硅顶点探测器（SVD-2）的触发系统，并在提高SVD-2的性能作出了很大贡献。

项目成果

K.Abe, et al.: "Observation of Large CP Violation in the Neutral B"Phys. Rev. Lett.. 87. 019802-1-7 (2001)

K.Abe 等人：“中性 B 中大 CP 破坏的观察”Phys。

K.Abe, et al.: "Determenation of 1Vcblusing the semileptonic decay B→D^+e^-v"Phys. Lett. B. 526. 247-257 (2002)

K.Abe 等人：“使用半轻衰变 B→D^+e^-v 测定 1Vcbl”Phys. B. 526. 247-257 (2002)

K.Abe et al.: "Measurement of Br(B^^-o→D^+l^-v^^-)and determination of 1Vecbl"Phys. Lett. B. 526. 258-268 (2002)

K.Abe 等人：“Br(B^^-o→D^+l^-v^^-) 的测量和 1Vecbl 的测定”Phys B. 526. 258-268 (2002)

K.Abe et al.: "Improved Measurement of Mixing-Induced CP Violation in the neutral B Meson System"Phys.Rev.. D66. 071102(R) (2002)

K.Abe 等人：“中性 B 介子系统中混合引起的 CP 破坏的改进测量”Phys.Rev..D66。

Y.Zhang et al.: "Measurement of B0-B0bar mixing rate with B0(B0bar)→D^<*+>π^+ partial Reconstruction"Phys.Rev.D to be published. (2002)

Y.Zhang等人：“测量B0-B0bar混合率与B0(B0bar)→D^<*+>π^+部分重建”Phys.Rev.D即将出版(2002)。