Physics of CP Violation at the Tevatron

CDF合作研究了质心能量为1.8 TeV的质子-反质子碰撞，使用美国巴达维亚费米国家加速器实验室（Fermilab）的Tevatron对撞机，自1985年首次观察到碰撞以来。CDF在1996年完成了它的最后一次物理运行（运行I），下一次运行（运行II）计划于2001年春季开始，运行II将使用升级的探测器沿着更高的亮度，运行II中最重要的物理课题之一将是详细研究B强子系统中的CP破坏现象。它将为基本粒子的标准模型提供一个检验，包括作为CP破坏起源的Kobayashi-Maskawa理论的有效性。CDF TOF计数器将在B强子的研究中发挥关键作用。我们与滨松光电共同开发并批量生产了TOF计数器用光电倍增管。整个TOF计数器的建造是与其他研究所的研究人员密切合作进行的，包括费米实验室和美国宾夕法尼亚大学。光电倍增管的原型于1999年7月在高能加速器研究组织KEK进行了1.4 T磁场下的性能测试。1999年7月开始批量生产，所有这些都以类似的方式进行了测试。它们已经被运送到费米实验室并安装在CDF探测器中。目前，TOF计数器已完成，除了读出电子设备，这将在未来几个月内安装。沿着TOF探测器的建设，我们已被雇用的事件重建程序和物理分析的发展。

The CDF collaboration has studied proton-antiproton collisions at a center-of-mass energy of 1.8 TeV, using the Tevatron collider at Fermi National Accelerator Laboratory (Fermilab) in Batavia, USA, since its first collisions observed in 1985. CDF finished its last physics run (Run I) in 1996, and the next run (Run II) is scheduled to begin spring 2001 with an upgraded detector along with a higher luminosity provided by the also upgraded accelerator complex.One of the most important physics topics in Run II will be a detailed study of CP violation phoenomena in the B hadron system. It would provide a test of the Standard Model of elementary particles, including the validity of the Kobayashi-Maskawa theory as the origin of CP violation.The CDF TOF counter will play a crucial role in the study of B hadrons. We have developed and mass-produced the photomultiplier tubes for the TOF counter together with Hamamatsu Photonics. The construction of the TOF counter as a whole has been performed with a close collaboration with researchers from other institutes, including Fermilab and the University of Pennsylbania, USA.The prototype photomultiplier tubes was tested in July 1999 for performance in a 1.4 T magnetic field at the High Energy Accelerator Research Organization, KEK.The mass production started in July 1999, and all of them have been tested in a similar fashion. They have been shipped to Fermilab and installed in the CDF detector. At this moment, the TOF counter is complete except for readout electronics, which will be installed in the coming months.Along with the TOF detector construction, we have been employed in development of event reconstruction programs and physics analyses.