Collaborative Research: The DarkSide Dark-Matter Search Using Liquid Argon

合作研究：使用液氩进行暗物质搜索

• 批准号: 2310042
• 负责人: Andrea Pocar
• 金额: $ 44万
• 依托单位: University of Massachusetts Amherst
• 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: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2310042&HistoricalAwards=false
• 关键词: Collaborative; Research; DarkSide; Dark; Matter

A large body of astronomical observations, including galactic rotation curves, strong gravitational lensing, and the anisotropy of the cosmic microwave background, indicates that known matter only accounts for a small fraction of the observed mass-energy of the Universe. A strong candidate for the remaining mass is weakly interacting Dark Matter particles with properties different from ordinary matter. Direct (non-gravitational) detection of dark matter would be a transformational discovery and would represent a watershed moment in the history of science, opening the gates to the investigation of the dark universe. The goal of this award is the testing, on-site installation, commissioning, and transitioning to operations of DarkSide-20k (DS-20k), an experiment capable of pushing the sensitivity of direct dark matter searches beyond that of any current or presently funded experiment. Broader scientific and technological impacts from the project include, among others: the production of low-radioactivity underground argon (UAr) for DS-20k and for nuclear test ban verification and radiometric dating; the continued study of the underground gas source discovered during the UAr exploration, a source which supplies 15 % of the current U.S. helium consumption; and the continued development of 3Dπ, a LAr-based TOF-PET system that can enhance cancer screening while lowering radiation dose.A leading dark matter candidate is a weakly interacting massive particle, or WIMP, a thermal relic of the Big Bang that has a sub-electroweak-scale self-annihilation cross section and a mass in the GeV/c2 to TeV/c2 range. The motion of galactic halo WIMPs relative to a detector on Earth could result in WIMP-nucleus elastic collisions detectable by a low-background, low-energy-threshold detector capable of unambiguously identifying a small number of nuclear recoils from WIMP collisions over the course of a very large exposure. Thanks to its excellent ionization response and unique scintillation light emission characteristics, liquid argon can provide outstanding sensitivity for WIMP-nuclear collisions and strong background suppression. The U.S. NSF groups involved in this program have led the conception and development of the DarkSide-20k liquid argon dark matter search. With support from a separate Mid-scale award, they are responsible for the construction and delivery of the most critical DS-20k components: the liquid argon time projection chamber (LAr TPC) that serves as the heart of the DS-20k dark matter detector along with its critical ancillary components, including the high-voltage delivery system, and the associated cryogenic, purification, and calibration systems. The U.S. NSF groups are also leading the activities for the procurement of the required ultra-low radioactivity argon, which is extracted from a special underground source in Colorado, with support from other US and international funding agencies (U.S. Department of Energy, Istituto Nazionale di Fisica Nucleare of Italy, and Canada Foundation for Innovation). This award will support the U.S. groups for the final testing, on-site installation, commissioning, and transition to operations of the DS-20k detector and preparation for science analyses. The DarkSide-20k experiment will utilize a two-phase time projection chamber with a 50-tonne fill (20-tonne fiducial) to extend the exploration for dark matter, reaching, in a 10 years run, a cross section of 4.9×10−48 cm2 for a 90 % C.L. exclusion and 1.6×10−47 cm2 at a 5 σ discovery significance for a 1 TeV/c2 WIMP, well beyond any current or presently funded experiment. This will lead to either discovery, confirmation, or exclusion of the WIMP dark matter hypothesis down to the level where coherent scatters from atmospheric neutrinos become an unavoidable background. DarkSide-20k will also be sensitive to a galactic supernova neutrino burst originating anywhere in the Milky Way Galaxy.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.

大量的天文观测，包括星系自转曲线、强引力透镜和宇宙微波背景的各向异性，表明已知物质只占宇宙观测质量能量的一小部分。剩余质量的有力候选者是具有不同于普通物质性质的弱相互作用的暗物质粒子。对暗物质的直接(非引力)探测将是一项变革性的发现，将代表着科学史上的一个分水岭时刻，为研究暗宇宙打开大门。该奖项的目标是测试、现场安装、调试和过渡到暗面-20k(DS-20k)的运行，这是一项能够推动直接暗物质搜索的灵敏度超过任何当前或目前资助的实验的实验。除其他外，该项目产生的更广泛的科学和技术影响包括：生产用于DS-20K以及用于禁止核试验核查和放射性测年的低放射性地下气体(UAR)；继续研究在UAR勘探期间发现的地下气源，该气源供应目前美国氦消费的15%；以及3DWIMP的继续开发，这是一种基于激光的飞行时间-正电子发射计算机断层扫描系统，可以在降低辐射剂量的同时增强癌症筛查。一个领先的暗物质候选是弱相互作用的大质量粒子，或称π，它是大爆炸的热遗迹，具有亚电弱尺度的自湮灭截面，质量在Gev/c2到Tev/c2范围内。银晕WIMP相对于地球上的探测器的运动可能导致WIMP-核的弹性碰撞，可以被一种低本底、低能量阈值的探测器探测到，该探测器能够明确地识别在非常大的曝光过程中WIMP碰撞产生的少量核反冲。由于其良好的电离响应和独特的闪烁光发射特性，液态Ar可以为WIMP-核碰撞提供卓越的灵敏度和强大的本底抑制。参与该计划的美国国家科学基金会小组领导了Darkside-20k液态Ar暗物质搜索的概念和发展。在一个单独的中型项目的支持下，他们负责建造和交付最关键的DS-20k部件：作为DS-20k暗物质探测器核心的液氮时间投影室(LAR TPC)及其关键的辅助部件，包括高压输送系统，以及相关的低温、净化和校准系统。美国NSF集团还在其他美国和国际资助机构(美国能源部、意大利国家核研究所和加拿大创新基金会)的支持下，领导从科罗拉多州的一个特殊地下来源提取所需的超低放射性Ar的活动。该合同将支持美国团队完成DS-20K探测器的最终测试、现场安装、调试和过渡运行，并为科学分析做准备。暗面-20K实验将利用一个带有50吨填充物(20吨基准点)的两相时间投影室来延长对暗物质的探索，在10年内达到4.9x10−48cm2的横截面(90%C.L.排除)和1.6x10−47cm2的5TeV/c2WIMP发现意义，远远超过任何现有或目前资助的实验。这将导致WIMP暗物质假说的发现、确认或排除，直到大气中微子的相干散射成为不可避免的背景。Darkside-20K还将对起源于银河系任何地方的银河系超新星中微子爆炸敏感。这一奖项反映了NSF的法定任务，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。