Construction of a Beam Test Prototype of the Hyper-K Water Cherenkov Detector to Control Systematic Errors for Leptonic CP Violation Measurements

为了使Hyper-K实验达到最高灵敏度，需要将系统误差控制在2%以内，主要误差来源是水切伦科夫探测器的模型、中微子-核相互作用的模型和中微子产生的模型。加拿大合作者提出了一个1千吨级水切伦科夫探测器，J-PARC E61（NuPRISM）探测器，位于距离J-PARC中微子源1公里处，以测量Hyper-K中微子-核相互作用的关键特征。为了使Hyper-K的系统误差达到2%，需要将Hyper-K和E61校准到1%的水平。在这里，我们提出了一个30吨的水切伦科夫实验被放置在费米实验室测试束设施（FTFB）的粒子动量范围从100 MeV/c到1200 MeV/c。该实验将为Hyper-K和E61中部署的校准系统和光电传感器提供测试平台。利用已知粒子类型、能量和轨迹的射束，可以测试检测器到1%水平的校准，并且可以根据需要对校准系统进行改进。 此外，我们将为已经在FTBF中运行的EMPHATIC强子产生实验做出贡献，该实验将测量强子相互作用过程，这对于提供Hyper-K计划所需的精确中微子通量计算是必要的。 FTFB中的试验梁计划将作为与日本、美国、英国、波兰和意大利的国际合作进行。加拿大的贡献是光电传感器的开发、测试和控制。由加拿大合作开发的光电传感器是一种高分辨率的多光电倍增管（光电倍增管）模块，由19个3英寸直径的快速光电倍增管组成。光电倍增管通过丙烯酸窗观察探测器，高压和读出电子电路包含在容器中。多PMT模块的第一个原型，包括丙烯酸圆顶，容器和电子设备，正在使用现有的2018财年RTI拨款于2018/2019年进行组装和测试。在这里，我们建议完善的多PMT的设计，以实现生产就绪的设计和建立30的多PMT模块部署在测试梁实验。 与此同时，这笔赠款将支持对EMPHATIC强子产生实验的贡献，该实验将描述精确计算中微子产生所必需的强子-核相互作用过程。 EMPHATIC是日本、美国和加拿大之间的国际合作，每个国家都提供子探测器。气凝胶环形成像切伦科夫探测器的设计已经由TRIUMF和温尼伯大学开发，它将在该赠款下建造。 该探测器将提供动量高达8 GeV/c的正向粒子识别。

To achieve the full sensitivity of the Hyper-K experiment, it is necessary to control systematic uncertainties to the level of 2% or less. The primary sources of systematic error are on the modeling of the water Cherenkov detector, the modeling of the neutrino-nucleus interactions, and the modeling of neutrino production. Canadian collaborators have proposed a 1-kiloton scale water Cherenkov detector, the J-PARC E61 (NuPRISM) detector, located 1 km from the neutrino source at J-PARC to measure critical features of neutrino-nucleus interactions for Hyper-K. To achieve 2% systematic errors for Hyper-K, it is necessary to calibrate both Hyper-K and E61 to the level of 1%. Here, we propose a 30-ton water Cherenkov experiment to be placed in the Fermilab Test Beam Facility (FTFB) with particle momenta ranging from 100 MeV/c to 1200 MeV/c. This experiment will provide a test-bed for the calibration systems and photosensors that will be deployed in Hyper-K and E61. With a beam of known particle type, energy and trajectory, the calibration of the detector to the 1% level can be tested and improvements to the calibration systems can be made as necessary. Additionally, we will contribute to the EMPHATIC hadron production experiment already running in the FTBF, that will measure hadronic interaction processes that are necessary to provide the precise neutrino flux calculations necessary for the Hyper-K program. The test beam program in the FTFB will be carried out as an international collaboration with Japan, the United States, the United Kingdom, Poland and Italy. The Canadian contribution is the development, testing and contruction of photosensors. The photosensor, developed by the Canadian collaboration, is a high resolution multi-PMT (photomultiplier tube) module that consists of 19 3 inch diameter fast PMTs in a pressure tolerant vessel. The PMTs view the detector through an acrylic window, and high voltage and readout electronics circuits are contained in the vessel. The first prototypes of the multi-PMT module, including the acrylic dome, vessel and electronics are being assembled and tested in 2018/2019 using an existing FY2018 RTI grant. Here, we propose to refine the design of the multi-PMT to achieve a production-ready design and build 30 of the multi-PMT modules for deployment in the test beam experiment. In parallel, this grant will support the contribution to the EMPHATIC hadron production experiment that will characterize the hadron-nucleus interaction processes that are necessary to make precision calculations of neutrino production. EMPHATIC is an interantional collaboration between Japan, the United States and Canada, with each country providing sub-detectors. The design for an aerogel ring imaging Cherenkov detector has been developed by TRIUMF and University of Winnipeg and it will be built under this grant. This detector will provide particle identification in the forward direction for momenta up to 8 GeV/c.