Direct Dark Matter Detection with the LUX-ZEPLIN Detector

LUX-ZEPLIN是第二代暗物质实验，将于2019/20年在位于美国南达科他州的桑福德地下研究设施部署和调试。它将使用10吨液体氙和500个光电倍增管（PMT）来探测暗物质与常规物质相互作用的极其罕见的事件。对于难以捉摸的暗物质粒子称为弱相互作用大质量粒子（WIMP）的明确检测，需要严格的检测器校准计划。该实验将使用一套内部分散的（83 mKr，131 He，220 Rn和CH 4标记的氚）和外部部署的密封中子（AmLi，205，206 BiBe，252 Cf，88 YeBe）和伽马（57 Co，22 Na，133 Ba，228 Th）辐射源，以提供对背景事件和WIMP信号响应的高统计校准。稀有事件实验需要精确校准的探测器以及根据现有校准数据调整的极其精确的模拟，以模拟探测器的响应。除了校准，所有数据分析步骤都必须非常稳健。一个非常重要的步骤是从脉冲序列中提取和识别单光子，数字化仪从包括PMT、电缆、放大器板和进一步电缆的电子链中记录单光子。这样做的算法存在，并已在适合现有实验的水平上进行了测试，但是，可以通过结合新技术和扩展的探测器响应的细节的理解，进一步改进。本项目的目标是进行详细的模拟，以提供最佳的理解的探测器响应校准源。该项目的目标是模拟LZ实验中使用的中子和伽马源的事件，并重建事件的位置和能谱，这是探测器校准的一个关键部分。改进光子探测、重建和触发工作将涉及生成氙时间投影室中的特定事件的模拟（例如，重新使用校准事件）、来自先前实验中记录的数据的事件以及使用可用的所有可能信息，以便提供和验证适当增强的算法。该项目的新奇是通过关注迄今为止尚未被模拟和分析所涵盖的探测器元件来确保的，这些元件要么完全没有被模拟和分析所涵盖，要么只是部分地被模拟和分析所涵盖。该项目还有一个新的方面，与未来的光子传感设备有关，这是一个与牛津实验室的实验能力理想匹配的领域。这将涉及为未来的暗物质探测器开发低温电子和电缆解决方案。这项研究的一个关键的新元素将是集成的电子读出链等传感器，建立在以前的工作在牛津大学，开发了一个探测器的电子响应model.The项目主要是基于计算机，使用GEANT为基础的模拟，根数据分析包和LZAp分析框架。它是在LZ协作范围内进行的，牛津大学是该协作的成员。硬件开发的一小部分将在牛津进行，主要是与帝国理工学院伦敦、布里斯托和利物浦合作。

LUX-ZEPLIN is a generation-2 Dark Matter experiment being deployed and commissioned in 2019/20 at the Sanford Underground Research facility in Lead, South Dakota (USA). It will use 10 tonnes of liquid xenon and 500 photomultiplier tubes (PMT) to detect extremely rare events of dark matter interactions with regular matter. For the unambiguous detection of the elusive dark matter particle called Weakly Interacting Massive Particle (WIMP) a rigorous detector calibration programme is required. The experiment will use a suite of internally dispersed (83mKr, 131Xe, 220Rn and CH4 labelled tritium) and externally deployed sealed neutron (AmLi, 205, 206BiBe, 252Cf, 88YeBe) and gamma (57Co, 22Na, 133Ba, 228Th) radiation sources to provide high statistics calibration of the response to background events and WIMP signal. Rare-event experiments require exquisitely a well-calibrated detector as well as extremely accurate simulations tuned on existing calibration data, to model the detector response. In addition to the calibrations, all data analysis steps have to be extremely robust. A very important step is to extract and identify single photons from the pulse trains that the digitizers record from the electronics chain comprising PMT, cabling, amplifier board and further cabling. Algorithms to do this exist and have been tested at a level suitable for existing experiments, however, further improvements can be made by incorporating new techniques and the expanded understanding of detail of the detector response.The goal of this project is to perform detailed simulations to provide an optimal understanding of the detector response to calibration sources. The project objective is to simulate events from neutron and gamma sources used in the LZ experiment and reconstruct events' position and energy spectra, which is a key part of the detector calibration. Improving on photon detection, reconstruction and triggering effort will involve generating simulations of particular events in a xenon time projection chamber (re-using calibration events, for example), events from data recorded in previous experiments and using all possible information that is available in order to provide and validate a suitably enhanced algorithms. Novelty of the project is ensured by focussing on detector elements that so far have not been covered by simulation and analysis, either not at all or only partially. There is a further novel aspects to the project that is related to future photon sensing devices, an area that is ideally matched to the experimental capabilities of the Oxford laboratory. This will involve developing cryogenic electronics and cabling solutions for a future dark matter detector. A crucial novel element of this research will be the integration of the electronic readout chain for such sensors, building on previous work at Oxford that developed a detector electronics response model.The project is mostly computer based, using GEANT-based simulation, the ROOT data analysis package and the LZAp analysis framework. It is carried out within the LZ Collaboration of which Oxford is a member. The small element of hardware development will be carried out at Oxford, mainly, in collaboration with Imperial College London, Bristol and Liverpool.