LZ Dark Matter Search

多次天文观测已经证实，宇宙中大约85%的物质不是由已知粒子构成的。破译这种所谓的暗物质的本质对宇宙学、天体物理学和高能粒子物理学至关重要。一个主要的假设是，它是由大爆炸后瞬间产生的弱相互作用大质量粒子（wimp）组成的。如果wimp是暗物质，那么它们在我们星系中的存在可以通过位于地下深处的探测器的原子核散射来检测，以帮助排除宇宙射线造成的背景。LZ是一个重约7吨的液态氙（LXe）暗物质探测器，将被安装在位于南达科他州铅市的桑福德地下研究设施（SURF）的4850英尺高的地方，用于寻找暗物质。这项工作将有助于该探测器的设计。与LXe相关的技术的发展将在世界范围内使用贵重液体作为检测材料的越来越多的实验中得到应用。这些项目还将为研究生和本科生提供辐射探测、低温学和气体净化方面的技术培训。LXe在天体物理学、国土安全和医学成像的伽马射线成像方面有实际应用。该探测器将使用已建立的液态氙时间投影室技术，通过读取初级和次级闪烁信号进行粒子识别，以及三维位置重建来利用液态氙的自屏蔽，去除表面伪影，并校准位置相关的响应函数。该设计还以装载钆的液体闪烁体为特色，它将密封地包围中央氙探测器，并提供强大的背景中子和伽马标记。LZ实验将对WIMP暗物质具有世界领先的灵敏度，灵敏度比目前的结果高400倍，并涵盖了大量理论上有动力的候选者。该奖项将提供资金，使该研究小组继续为LZ暗物质实验提供阴极高压输送系统的工作。

Multiple astronomical observations have established that about 85% of the matter in the universe is not made of known particles. Deciphering the nature of this so-called Dark Matter is of fundamental importance to cosmology, astrophysics, and high-energy particle physics. A leading hypothesis is that it is comprised of Weakly Interacting Massive Particles, or WIMPs, that were produced moments after the Big Bang. If WIMPs are the dark matter, then their presence in our galaxy may be detectable via scattering from atomic nuclei in detectors located deep underground to help reject backgrounds due to cosmic rays. LZ is a ~7-tonne liquid xenon (LXe) dark matter detector to be installed at the 4850-foot level of the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to look for dark matter. This work will contribute to the design of that detector. Development of technology related to LXe will find use in the increasing number of experiments worldwide using noble liquids as detection materials. These projects will also result in technical training in radiation detection, cryogenics, and gas purification for graduate and undergraduate students. LXe has practical applications to gamma ray imaging for astrophysics, Homeland Security, and medical imaging.This detector will use established liquid xenon time projection chamber technology with readout of primary and secondary scintillation signals for particle identification, together with 3-D position reconstruction to exploit the self-shielding of the liquid xenon, removal of surface artifacts, and calibration of position-dependent response functions. The design also features a gadolinium-loaded liquid scintillator veto that will hermetically enclose the central xenon detector and provide powerful tagging of background neutrons and gammas. The LZ experiment will have world-leading sensitivity to WIMP dark matter with a sensitivity about 400 times better than current results and covering a substantial range of theoretically motivated candidates. This award will provide funding to enable this research group to continue to contribute to the LZ dark matter experiment with work on the cathode high voltage delivery system.