Study of Photon Detector in Beam for the Rare K^+ Decay at Rest Experiment

束中光子探测器用于稀有K^静止衰变实验的研究

• 批准号: 11640296
• 负责人: SATO Takahiro
• 金额: $ 0.96万
• 依托单位: High Energy Acceleration Research Organization
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640296/
• 关键词: rare kaon decay; kaon decay at rest; photon detector; pure CsI Crystal; wavelength shifter fiber; K中間子稀崩壊; ガンマ線検出器; K^+静止実験; 大強度

The search for the rare kaon decay K^+→π^+νν^^- has been done in the kinematical region where the π^+ momentum is greater than the π^+ momentum from K^+→π^+π^0 decay which is the main background source. As one of the Japan-US Cooperative Projects, BNL-E787 experiment, searched for the K^+→π^+νν^^- from kaons decay at rest in this kinematical region and found one candidate event. We are now preparing E949 experiment as a Japan-US Cooperative Project. E949 experiment aims to find around ten events of K^+→π^+νν^^- decay. In order to do so, it is very important to search for the kinematical region where π^+ momentum is lower. In this kinematical region, photons from π^0 decay tend to be emitted to the direction of the incident K^+ beam. We have made a high statistics simulation to confirm it. This leads us to increase the photon detection efficiency in the direction of the incident beam. The photon detectors in this region should correctly work in the high intensity kaon beam and in the magnetic field of 1Tesla. As candidates of this kind of photon detector, the following two methods were designed.1) The pure CsI crystals with fine-mesh type photo-multipliers which can be used in the high magnetic field.2) The lead and plastic scintillator sandwich counter with wavelength shifter fiber read out to the normal photo-multipliers.In order to find the best design as the photon detector to suppress the K^+→π^+π^0 background, two designs were studied by computer simulations and performance tests of the prototype detectors.

对罕见的 kaon 衰变 K^+→π^+νν^^- 的搜索是在运动学区域中完成的，其中 π^+ 动量大于来自 K^+→π^+π^0 衰变的 π^+ 动量，这是主要背景源。作为日美合作项目之一的BNL-E787实验，在这个运动区域从静止的kaons衰变中寻找K^+→π^+νν^^-，并找到了一个候选事件。我们现在正在准备E949实验作为日美合作项目。 E949实验旨在寻找大约十个K^+→π^+νν^^-衰变事件。为此，寻找 π^+ 动量较低的运动学区域非常重要。在这个运动学区域中，来自 π^0 衰变的光子倾向于向入射 K^+ 光束的方向发射。我们做了一个高统计模拟来证实这一点。这使得我们提高了入射光束方向上的光子探测效率。该区域的光子探测器应在高强度 kaon 光束和 1 特斯拉的磁场中正确工作。作为这种光子探测器的候选，设计了以下两种方法。1）带有细网型光电倍增管的纯CsI晶体，可在强磁场中使用。2）带有波长移动光纤的铅和塑料闪烁体夹层计数器读出到普通光电倍增管。为了找到抑制K^+→π^+π^0背景的最佳光子探测器设计，两种方法 通过计算机模拟和原型探测器的性能测试对设计进行了研究。

项目成果

小中哲,中野貴志,新川孝男: "K^+中間子の稀崩壊K^+→π^+υυの発見"日本物理学会誌. 55・11. 838-845 (2000)

Satoshi Konaka、Takashi Nakano、Takao Shinkawa：“K^+介子的罕见衰变K^+→π^+υυ”日本物理学会杂志55・11（2000）。

小中哲,中野貴志,新川孝男: "K^+中間子の稀崩壊K^+→π^+νν^^-の発見"日本物理学会誌. 55・11. 838-845 (2000)

Satoshi Konaka、Takashi Nakano、Takao Shinkawa：“K^+介子的罕见衰变K^+→π^+νν^^-”日本物理学会杂志55・11（2000）。

A.Konaka, et al.: "Evidence for the Decay K^+→π^+νν^^-."Butsuri. 55. 838-845 (2000)

A.Konaka 等人：“K^+→π^+νν^^- 衰变的证据”Butsuri。55. 838-845 (2000)

S. Adler: "Further Search for the Decay K^+→π^+νν^^-"KEK PREPRINT. 99-171. 1-10 (2000)

S. Adler：“进一步搜索衰变 K^+→π^+νν^^-”KEK 预印本。

T.Shinkawa: "Search for K^+→π^+νν^^- below Kπ2 at BNL E949."KEK Proceedings. 99-3. 137-140 (1999)

T. Shinkawa：“在 BNL E949 处搜索 Kπ2 下方的 K^+→π^+νν^^-”。KEK 99-3 (1999)。