The Outer Veto for the DarkSide-20k Dark Matter Search

DarkSide-20k 暗物质搜索的外部否决权

• 批准号: 2310091
• 负责人: Shawn Westerdale
• 金额: $ 51万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-15 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2310091&HistoricalAwards=false
• 关键词: Outer; Veto; DarkSide; 20k; Dark

An astronomical body of evidence indicates that 27% of the energy density of the universe is composed of dark matter — a form of matter that cannot be described by the Standard Model of particle physics and only weakly couples to the known particles. Dark Matter has clear gravitational effects evident in astrophysical and cosmological observations. A promising dark matter candidate is the Weakly Interacting Massive Particle (WIMP), a relic of the early universe with weak couplings to nucleons within atoms. A WIMP halo is expected to surround the entire galaxy including our solar system. The Earth’s motion relative to it creates a flux of WIMPs that may scatter on a target nucleus in the detector, creating a nuclear recoil. The DarkSide-20k experiment seeks to detect such WIMPs using a 50 tonne active volume of liquid argon (LAr) as part of a "dual-phase time projection chamber (TPC) detector", capable of completely suppressing electromagnetic backgrounds. As a result of these measurements, liquid argon detectors are capable of reaching large, nearly-background-free exposures. However, neutrons stand out as a remaining prominent background: they are produced in rare nuclear reactions in detector materials by cosmic-ray muons interacting with the detector and its environment. These cosmogenic neutrons are produced with high energies and can penetrate the detector shielding, potentially producing WIMP-like nuclear recoils in the detector. The work funded by this grant will finalize the design and carry out the implementation of the DarkSide-20k Outer Veto, and ensure the detector can operate free of cosmogenic neutron backgrounds. At the same time, this work will provide valuable hands-on training to students in detector design and instrumentation through prototyping and installation work, as well as in skills related to photoelectronics, data acquisition systems, and simulation and analysis tools needed to inform the detector design. The work will also develop 3D detector visualization tools for use in both outreach and in algorithm development.This project supports the work to be carried out by the University of California, Riverside group of the DarkSide-20k experiment, responsible for the design and implementation of the Outer Veto. This work will involve optical and mechanical simulations of the Outer Veto instrumentation to ensure its stability and that it meets the requirements needed to eliminate cosmogenic neutron backgrounds. Based on the simulation-informed design, a small-scale prototype detector will be built to test the optical and mechanical systems on campus before deploying them in the full detector. Additionally, cost-effective reflectors capable of covering large-area detectors with low photosensor coverage will be tested to ensure that they maintain their reflectance when submerged in liquid argon. In addition to the instrumentation, the work supported by this grant will carry out the design and implementation of the data acquisition and low-level data processing systems for the Outer Veto. The funded work will also complete the acquisition of the getter for the LAr TPC purification system. The outreach project funded by this experiment will involve programming a 3D headset to display an image of the DarkSide-20k detector and visualize various classes of signals occurring in it. This tool will be brought to outreach events around the Riverside area, shown to members of the community and at local schools, and it will provide a useful tool for algorithmic development while developing analysis tools for use in the DarkSide-20k dark matter search.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

天文证据表明，宇宙 27% 的能量密度是由暗物质组成的，暗物质是一种无法用粒子物理学标准模型描述的物质形式，仅与已知的暗物质存在弱耦合。天体物理学和宇宙学观测中明显的引力效应是弱相互作用大质量粒子（WIMP），它是早期宇宙的遗迹，与原子 A 内的核子具有弱耦合。 WIMP 光环预计将围绕整个星系，包括我们的太阳系。地球相对运动会产生大量 WIMP 粒子，这些粒子可能会散射到探测器中的目标核上，从而产生核反冲力，DarkSide-20k 实验旨在探测此类粒子。 WIMP 使用 50 吨活性液氩 (LAr) 作为“双相时间投影室 (TPC) 探测器”的一部分，能够完全抑制电磁背景 As。这些测量的结果是，液氩探测器能够达到大的、几乎无背景的曝光，然而，中子作为剩余的突出背景脱颖而出：它们是由宇宙射线μ子与探测器材料中的罕见核反应产生的。这些宇宙中子产生的能量很高，可以穿透探测器的屏蔽层，有可能在探测器中产生类似 WIMP 的核反冲力，这笔赠款资助的工作将最终确定设计并进行。实施 DarkSide-20k 外否决，并确保探测器能够在没有宇宙中子背景的情况下运行。同时，这项工作将通过原型设计和安装工作为学生提供探测器设计和仪器仪表方面的宝贵实践培训。以及与光电、数据采集系统以及探测器设计所需的模拟和分析工具相关的技能。这项工作还将开发用于推广和算法开发的 3D 探测器可视化工具。该项目支持这项工作将由加州大学河滨分校的 DarkSide-20k 实验小组进行，负责 Outer Veto 的设计和实施。这项工作将涉及 Outer Veto 仪器的光学和机械模拟，以确保其稳定性。它满足消除宇宙中子背景所需的要求，基于模拟信息设计，将建造一个小型原型探测器，以在校园内测试光学和机械系统，然后再将其部署到完整的探测器中。将测试能够覆盖具有低光电传感器覆盖率的大面积探测器的经济有效的反射器，以确保它们在浸没在液氩中时保持其反射率。除了仪器之外，这笔赠款支持的工作还将进行设计和实施。资助的工作还将完成 LAr TPC 净化系统的吸气剂的采购。该实验资助的外展项目将涉及对 3D 耳机进行编程。显示 DarkSide-20k 探测器的图像并可视化其中发生的各种信号。该工具将被带到河滨地区周围的外展活动中，向社区成员和当地学校展示，它将提供一个有用的工具。用于算法开发，同时开发用于 DarkSide-20k 暗物质搜索的分析工具。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。