Study of Symmetry in Kaon Decays

Kaon衰变的对称性研究

• 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
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08044100/
• 关键词: T-violation; CP-violation; K_<mu3> decay; transverse polarization; stopped kaon; superconducting toroidal spectrometer; KEK-PS; CsI (TI); μ^+横偏極; K^+中間子

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.

KEK-PS的E246国际合作小组通过对K^+*pi^0mu^+nu衰变中的横向μ子偏振P_T的高精度测量来寻找时间反转不变性(T)违反。P_T的非零值将是违反t的明显证据。在这种带电介子衰变中，末态相互作用产生的伪效应很小。另外，标准模型对P_T的贡献可以忽略不计。因此，P_T对超出标准模型的cp违背机制非常敏感。多重希格斯双重态或轻夸克和超对称模型是目前感兴趣的。实验使用了一个停止的K^+光束和一个超导环形光谱仪。停止K^+可以覆盖整个衰减运动学区域。结合环面30‰的旋转对称性，几乎消除了所有的系统误差。该探测器由含256根闪烁光纤的有源目标和环形计数器系统组成，含768个CsI （TI）晶体的pi^0探测器，含4个线室的μ子跟踪系统，含4个TOF计数器系统和5个μ子偏振计组成。P_T测量为偏振计中衰变正电子的顺时针/逆时针不对称性。数据采集始于1996年。在数据采集初期，验证了探测器的良好性能。正电子时间谱包含一个非常小水平的时间无关背景。对于π ^0的辨识，可以分析双光子和单光子事件。1996年和1997年的数据正在分析中。初步结果表明，违反t参数Imxi与零一致，统计精度为2 × 10^<-2>，超过了之前BNL-AGS的限制。实验数据表明，系统误差比统计误差小得多。

项目成果

今里純: "Search for T-violation in the K^+→π^0μ^+ν decay" Frascati Physics Series. (1997)

Jun Imazato：“在 K^+→π^0μ^+ν 衰变中寻找 T 破坏”弗拉斯卡蒂物理系列（1997）。

今里純,久野良孝Y.Kudenko,その他: "CsI (Tl) π^0-detector for experiments on the search for T-violation in the Kaou decay" Instruments and Experimental Techniques. 39・2. 164-172 (1996)

Jun Imazato、Y.Kudenko 等人：“用于在 Kaou 衰变中寻找 T 破坏的实验的 CsI (Tl) π^0 探测器”仪器和实验技术 39・2 (1996)。

R.L.Wixted, S.Chidzik, D.R.Marlow, C.R.Mindas, S.Sekikawa, I.Arai, A.Suzuki, A.Watanabe, Y.Kuno: "A 32-channel Waveform Sampling Fastbus Module with Local DSP Prodessing" Nuclear Instruments and Methods. A386. 483 (1997)

R.L.Wixted、S.Chidzik、D.R.Marlow、C.R.Mindas、S.Sekikawa、I.Arai、A.Suzuki、A.Watanabe、Y.Kuno：“具有本地 DSP 处理功能的 32 通道波形采样快速总线模块”核仪器和

T.Ikeda, M.D.Chapman, Y.Igarashi, J.Imazato, J.M.Lee, M.M.Khabibullin, O.V.Mineev, H.S.Shimizu, S.Shimizu, A.Suzuki, A.Watanabe, and T.K.Yokoi: "High-precision magnetic field mapping with a three-dimensional Hall probe for a T-violation experiment in K_<m

T.Ikeda、M.D.Chapman、Y.Igarashi、J.Imazato、J.M.Lee、M.M.Khabibullin、O.V.Mineev、H.S.Shimizu、S.Shimizu、A.Suzuki、A.Watanabe 和 T.K.Yokoi：“高精度磁场测绘

D.Dementyev,今里純,Y.Kudenko他: "CsI (Tl) calorimeter with photodiode readout to search for T-violation in K_<μ3> decay" Nuclear Instruments and Methods. A379. 499-501 (1996)

D. Dementyev、Jun Imazato、Y. Kudenko 等人：“带有光电二极管读数的 CsI (Tl) 热量计，用于搜索 K_<μ3> 衰变中的 T 破坏”核仪器和方法 A379（1996）。