Study of T-invariance in K^+ Decay at KEK Proton Synchrotron

本课题的目的是研究时间反转不变性（TRI）问题，并在K^+ *pi^0mu^+nu的K - K衰变过程中寻找其违逆性。我们利用KEK质子同步加速器上的超导环形谱仪寻找了表明违背TRI的横向介子极化。该研究有助于揭示cp -违逆的起源，这是当前粒子物理学的重要问题之一。这个项目是由日本、俄罗斯（俄罗斯科学院核研究所）和加拿大（TRIUMF和其他机构）的国际合作进行的。虽然实验本身是KEK-PS实验之一，但由于实验规模较大，我们花了数年时间通过国际合作来建造和准备探测器。1995年完成实验装置并开始测量。探测器的主要元件之一是光子探测器，用于从K^+*pi^0mu^+nu衰变中检测pi^0。该探测器由768个CsI（Tl）晶体组成，由日俄合作设计。晶体在乌克兰的Kharikov在INR的指导下生产，并送到KEK，在那里进行进一步的准备。一桶CsI（Tl）于1995年完成，经过仔细的测试、调整和校准测量，于去年9月安装在环形光谱仪上。日本-加拿大合作制造了一个主动目标和一个跟踪室C1。他们在TRIUNF商店组装，并于去年夏天带到KEK。它们也被安装在安装和调优中。整个实验装置于去年秋天准备就绪，系统的测试和调谐开始使用KEK-PS的K5的K^+光束。通过测量K^+*pi^0pi^+和K^+*mu^+nu衰减来实现CsI（Tl）晶体的增益调整。对介子偏振计的设计进行了测量，如衰减器厚度等。正电子计数器被仔细地排列，它们的阈值被调整。在这些准备测量之后，1996年1月开始了对介子极化的实际测量。该测量将在下一财政年度继续进行，以使结果具有足够的统计准确性。但是我们开始对采集的数据进行分析。少

The purpose of this project is to study the problem of time reversal invariance (TRI) and to search for its violation in a kaon decay process K^+ *pi^0mu^+nu.We looked for transverse muon polarization which indicates violation of TRI by using the Superconducting Toroidal Spectrometer at the KEK proton synchrotron. This study can shed light to the origin of CP-violation which is one of the important issues of the present particle physics.This project was carried out by an international collaboration of Japan, Russia (Instutute for Nuclear Research, Russian Academy of Sciences) and Canada (TRIUMF and others).Although the experiment itself is one of the KEK-PS experiments, we spent years to construct and preapre the detector by international cooperative work, because the size of the experiment is large.In 1995 experimental apparatus was completed and measurement was started.The one of the mail elemens of the detector is a photon detector to detect pi^0 from the K^+*pi^0mu^+nu decay.This d … More etector is comprise 768 CsI(Tl) crystals and was designed by Japan-Russia collaboration.The crystals were produced at Kharikov in Ukraina under the conduct of INR,and brought to KEK where further preparation has been done. A barrel of CsI(Tl) was completed in 1995 and was installed at the Toroidal Spectrometer in last September after a careful test, tuning and a calibration measurement.An active target and one of the tracking chambers, C1, have been made by the Japan-Canada collaboration.They were assembled at the TRIUNF shop and brought to KEK last summer.They were also installed in the setup and tuned.The whole experimental apparatus became ready in last fall and the test and tuning of the system was started using K^+ beam from K5 at KEK-PS.The gain adjustment of CsI(Tl) crystals was performed by the measurement of K^+*pi^0pi^+ and K^+*mu^+nu decays.The measurement was also done for the design of the muon polarimeter, such as the degrader thickness.The positron counters were carefully aligned and their threshold was tuned.After these preparation measurements, a real measurement of the muon polarization started in January 1996.The measurement will continue further in next fiscal year to get enough statistical accurscy in the result.But we started the analysis of taken data. Less