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

本项目的目的是研究KEK质子同步加速器上的时间反转不变性(TRI)问题，并在K^+*pi^0µ^+nuK介子衰变过程中寻找时间反转不变性(TRI)的破坏。这项研究可以揭示CP破坏的起源，这是当前粒子物理的重要问题之一。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等)等国际合作进行的。虽然实验本身是KEK-PS实验之一，但我们花了数年时间通过国际合作建造和制备探测器，由于实验规模较大，实验装置于1995年建成并开始测量。探测器的主要元件之一是一个光子探测器，用于从K^+*pi^0？+nu衰变中探测pi^0。这个d…更多的刻蚀器由768个CsI(Tl)晶体组成，由日俄合作设计。晶体在乌克兰的Kharikov由INR生产，并被带到KEK，在那里做了进一步的准备工作。一桶CsI(Tl)在1995年完成，并在经过仔细的测试、调谐和校准测量后于去年9月安装在环面光谱仪上。它们是由日本和加拿大合作制造的。它们是在TRIUNF工厂组装的，并于去年夏天运到KEK。它们也安装在安装和调试中。整个实验装置在去年秋天准备就绪，开始用K5的K^+束流对系统进行测试和调试。通过测量K^+*pi^0pi^+和K^+*mu^+nu衰减率来调整CsI(Tl)晶体的增益。还对介子偏振器的设计进行了测量，如衰减器的厚度。仔细地对准了电子计数器，并调整了它们的阈值1996年1月，我们开始了对介子极化的真正测量。为了获得足够的统计精度，测量将在下一财年继续进行。但我们开始了对所取数据的分析。较少

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