The Belle-II Electromagnetic Calorimeter Endcap

Belle-II将在位于日本KEK实验室的高亮度SuperKEKB e+e对撞机上探测粒子物理的风味部分。物理操作将于2016年底开始，目标是到2022年收集前两代b工厂（SLAC的PEP-II和KEK的KEKB）综合光度的30倍。这个精密前沿设施将打开一个令人兴奋的窗口，在新的能量尺度上超越现有的对撞机，包括大型强子对撞机，凭借量子环修正对大质量的，尚未发现的粒子敏感。这些假设的粒子在涉及底夸克、粲夸克和τ轻子的过程的精确测量中表现出来，比如CP破坏和其他不对称、罕见的衰变，以及我们目前对物理学的理解中禁止的过程。这个项目是对大型强子对撞机直接搜索新物理的补充。所要求的资金将使加拿大小组能够最后确定该小组提供的探测器硬件所需的研究，并为提供全部硬件开发工具和专门知识。Belle- ii将开始使用Belle公司的掺铊碘化铯（CsI(Tl)）闪烁量热计进行数据采集，该量热计配备了新的数字化和特征提取电子设备。该量热计具有良好的性能，但闪烁时间常数较慢（1微秒）。当SuperKEKB的光度增加时，光束相关背景的高占位率将导致前端盖量热计的性能显著下降。作为对Belle-II探测器的贡献，加拿大小组提议将前端帽的高占用区域升级为纯CsI。纯CsI比CsI（Tl）快得多，因此对背景的敏感度要低得多。然而，它的光产率要低得多。为了处理快脉冲、低光产率和大动态范围的特性，CsI晶体将使用不同于现有量热计的光传感器、放大器、数字化仪和特征提取算法。加拿大集团将负责该项目的所有方面，包括采购晶体和光电倍增管；开发和构建放大器、数字化和特征提取电子设备；校正系统及程序；以及对机械和冷却系统的修改。我们正在申请资金，用于开发和测试25个晶体阵列以及相关的光电传感器和电子设备，约占整个项目的8%。这将使我们能够完成对读出系统的研发，并验证我们提出的解决方案在测试光束环境中满足系统级的要求。它还将使我们能够制定晶体和光电管采购协议，包括验证规格所需的设备和工具。了解光束相关的背景是项目的重要组成部分。Belle-II正在开发一套探测器，将于2015年1月安装，这些探测器将在SuperKEKB调试期间量化背景，并进行模拟比较。我们已经向合作提出，这一套应该包括热中子探测器，因为这个背景组件决定了现有的量热计读出电子设备的寿命，以及其他Belle-II探测器系统的寿命，并且是量热计占用的一个显着组件。它也是最难精确模拟的部件。我们正在申请资金用于He-3中子计数器进行这项测量。

Belle-II will probe the flavour sector of particle physics at the high-luminosity SuperKEKB e+e- collider, located at the KEK laboratory in Japan. Physics operations will start in late 2016, with the goal of collecting by 2022 thirty times the combined integrated luminosity of the two previous generation B-factories, PEP-II at SLAC and KEKB at KEK. This precision-frontier facility will open an exciting window on new energy scales beyond the reach of existing colliders, including the LHC, by virtue of quantum loop corrections that are sensitive to massive, and as yet undiscovered, particles. These hypothesized particles manifest themselves in precision measurements of processes involving bottom and charm quarks and tau leptons, such as CP violation and other asymmetries, rare decays, and processes that are forbidden within our current understanding of physics. This program is complementary to direct searches for new physics at the LHC. The funds requested will enable the Canadian group to finalize the research needed for the group's detector hardware contribution, and to develop the tools and expertise for the full hardware contribution. Belle-II will start data taking with the thallium-doped cesium iodide (CsI(Tl)) scintillator calorimeter from Belle, outfitted with new digitizing and feature-extraction electronics. This calorimeter had very good performance, but has a slow scintillation time constant (1 microsecond). At the increased luminosity of SuperKEKB, high occupancies from beam related backgrounds will cause significant deterioration of the performance of the forward endcap calorimeter. As its contribution to the Belle-II detector, the Canadian group is proposing to upgrade the high-occupancy regions of the forward endcap to pure CsI. Pure CsI is much faster than CsI(Tl), and is therefore much less sensitive to backgrounds. However, it has a much lower light yield. To deal with the characteristics of fast pulses, low light yield and large dynamic range, the CsI crystals will use different photosensors, amplifiers, digitizers, and feature-extraction algorithms than the existing calorimeter. The Canadian group will take responsibility for all aspects of this project, including procuring the crystals and photomultiplier tubes; developing and building the amplifiers, digitizing, and feature-extraction electronics; calibration systems and procedures; and modifications to the mechanical and cooling systems. We are requesting funds to develop and test a 25-crystal array together with the associated photosensors and electronics, approximately 8% of the full project. This will allow us to complete the R&D on the readout system, and verify that our proposed solutions satisfy the requirements at a system level in a test beam environment. It will also allow us to develop the crystal and phototube procurement protocols, including the equipment and tooling needed to verify the specifications. Understanding the beam-related backgrounds is an essential component of the project. Belle-II is developing a set of detectors to be installed in January 2015, which will quantify the backgrounds during the commissioning of SuperKEKB and enable comparisons to simulations. We have proposed to the collaboration that this set should include thermal neutron detectors, since this background component determines the lifetime of the existing calorimeter readout electronics, as well as that of other Belle-II detector systems, and is responsible for a noticeable component of the calorimeter occupancy. It is also the most difficult component to simulate accurately. We are requesting funds for He-3 neutron counters to undertake this measurement.