Study of Symmetry in Kaon Decays

Kaon衰变的对称性研究

基本信息

批准号：
08044100
负责人：
IMAZATO Jun
金额：
$ 4.61万
依托单位：
High Energy Accelerator Research Organization, Institute for Particle and Nuclear Studies
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

A Search for time-reversal invariance (T) violation, via a high precision measurement of the transverse muon polarization, P_T in the K^+*pi^0mu^+nu decay, was conducted by the E246 international collaboration at KEK-PS.A non-zero value of P_T would be clear evidence for T-violation. The spurious effect from final state interactions is small in this charged kaon decay. In addition, the standard model contribution to P_T is negligibly small. Hence P_T is very sensitive to mechanismes of CP-violation beyound the standard model. The multi-Higgs doublet or leptoquark and supersymmetric models are currently of interest.The experiment used a stopped K^+ beam and a Superconducting Toroidal Spectromer. With stopped K^+ the entire decay kinematics region could be covered. Combined with the 30ﾟ rotational symmetry of the toroid almost all systematic errors were cancelled. The detector consisted of 1) an active target with 256 scintillating fibers and a ring counter system, 2) a pi^0 detector with 768 CsI (TI) crystals, 3) a muon tracking system with four wire chambers, 4) TOF counter system, and 5) muon polarimeters. P_T was measured as the clockwise/counterclockwise asymmetry of decay positrons in the polarimeter.Data taking started in 1996. At an early stage of data taking, good detector performance was verified. The positron time spectra contained a very small level of time independent background. For pi^0 identification both two photon and single photon events could be analyzed. The data taken in 1996 and 1997 are under analysis. According to a preliminary result, the T-violating parameter Imxi is consistent with zero with a statistical accuracy of 2x10^<-2> superceding the previous limit from BNL-AGS.Systematic errors have been shown to be much smaller than the statistical ones from the experimental data.

通过高精度测量的横向muON极化，k^+*pi^0mu^0mu^+nu衰减中的p_t搜索时间反转不变性（t）违规，由kek-ps.-ps.a的e246国际协作进行了t-into Chiolation的e246国际协作，这是t-p_t的非零值的证据。在这个被带电的kaon衰减中，最终状态互动的虚假效果很小。此外，对P_T的标准模型贡献忽略不足。因此，P_T对CP侵略的机制非常敏感，标准模型BEYOUND。当前感兴趣的是多用途双打或Leptoquark和超对称模型。该实验使用了停止的k^+梁和超导环形光谱仪。随着k^+的停止，可以覆盖整个衰减运动学区域。结合环形的30°旋转对称性几乎所有系统误差都被取消。检测器由1）一个具有256个闪烁纤维的活性靶标和环形系统，2）具有768 CSI（TI）晶体的PI^0检测器，3）带有四个钢丝室的MUON跟踪系统，4）TOF Counter系统和5）Muon Pallerimterter。 P_T被测量为偏光仪中衰减电位的顺时针/逆时针不对称。DATA摄入于1996年。在数据获取的早期阶段，验证了良好的检测器性能。北极星时间光谱包含很小的时间独立背景。对于PI^0，可以分析两个光子和单个光子事件。在1996年和1997年获得的数据正在分析。根据初步结果，t-violation参数IMXI与零一致，统计精度为2x10^<-2>从BNL-AGS.STEMAGS的统计误差已显示出比从实验数据中的统计误差小得多。