Collaborative Research: DarkSide-20k: A Global Program for the Direct Detection of Dark Matter Using Low-Radioactivity Argon

合作研究：DarkSide-20k：使用低放射性氩直接探测暗物质的全球计划

• 批准号: 1812480
• 负责人: Laurie Williams
• 金额: $ 5万
• 依托单位: Fort Lewis College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1812480&HistoricalAwards=false
• 关键词: Collaborative; Research; DarkSide; 20k; Global

Multiple astronomical observations have established that about 85% of the matter in the universe is not made of normal atoms, but must be otherwise undetected elementary "dark matter" particles that do not emit or absorb light. 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. Direct detection of WIMP dark matter would solve a fundamental mystery in particle physics and cosmology, providing a unique window to learning about the primary matter constituent of the Universe and of physics beyond the Standard Model of particle physics. This award is to support the NSF-funded DarkSide (DS) groups for the construction and operation of DarkSide-20k (DS-20k), a direct WIMP search using a Liquid Argon Time Projection Chamber (LAr TPC) with an active (fiducial) mass of 23 tons (20 tons).The LAr TPC relies heavily on the utilization of argon obtained from underground sources, or UAr. The planned Aria project for UAr purification may improve the worldwide availability of valuable stable rare isotopes such as O-18, N-15, and C-13, used for various medical, industrial and energy generation applications. The production of hundreds of tonnes of low-radioactivity UAr for DS-20k and for other technical uses requiring detection of Ar-37 for nuclear test ban verification, and Ar-39, for radiometric dating. Special E&O programs are planned with focus on educating K-12 teachers about basic physics and how it relates to dark matter detection, re-starting a summer school experience for high-school and undergraduate students, as well giving research opportunities to undergraduate students at participating underrepresented-minority serving institutions.DS-20k builds on the success of DarkSide-50 (DS-50), operating at LNGS since 2013, which produced two zero-background science results using atmospheric argon (AAr) and then underground argon (UAr) fills. DS-50 demonstrated an 39Ar reduction of 1400 in the UAr. Electron recoil (ER) background was shown to be completely suppressed in the region of interest, with discrimination better than 1 part in 1.5 x 10^7. These results demonstrated the ability of large LAr TPCs to operate in an "instrumental background-free mode" - a mode in which less than 0.1 events (other than actual nuclear recoils from elastic scattering of atmospheric and diffuse supernova background neutrinos) are expected in the region of interest for the planned exposure of DS-20k. DS-20k will have ultra-low backgrounds, with the ability to measure its backgrounds in situ, and sensitivity to WIMP-nucleon cross sections of 1.2 x 10^-47 cm2 (1.1 x 10^-46 cm2) for WIMPs of 1 TeV/c2 (10 TeV/c2) mass, to be achieved during a 5 yr run with exposure of 100 t yr.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.

多项天文观测已经证实，宇宙中约85%的物质不是由正常原子组成，而是必须是不发射或吸收光线的、未被探测到的原生“暗物质”粒子。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具有根本的重要性。一个主要的假设是，它是由相互作用很弱的大质量粒子组成的，这些粒子是在大爆炸后不久产生的。如果WIMP是暗物质，那么它们在我们银河系中的存在可能是通过位于地下深处的探测器中原子核的散射来检测到的，以帮助排除宇宙射线的背景。直接探测WIMP暗物质将解开粒子物理学和宇宙学中的一个基本谜团，为了解宇宙的主要物质组成和超越粒子物理标准模型的物理学提供了一个独特的窗口。这项奖励是为了支持美国国家科学基金会资助的Darkside-20k(DS-20k)项目的建造和运营，这是一项使用主动(基准)质量为23吨(20吨)的液态Ar时间投影室(Lar TPC)进行的直接WIMP搜索。Lar TPC严重依赖于从地下来源获得的Ar的利用。计划中的Aria UAR提纯项目可能会改善有价值的稳定稀有同位素的全球可获得性，如O-18、N-15和C-13，用于各种医疗、工业和能源发电应用。生产数百吨低放射性UAR，用于DS-20K和其他技术用途，需要检测Ar-37用于禁止核试验核查，Ar-39用于放射性年代测定。特别的E&Amp；O计划的重点是教育K-12教师基础物理以及它与暗物质探测的关系，为高中生和本科生重新开始暑期学校体验，并为参与的少数族裔服务机构的本科生提供研究机会。DS-20k建立在Darkside-50(DS-50)成功的基础上，自2013年开始在LNGS运行，它产生了两个使用大气AAR(AAR)和地下AAR(UAR)填充的零背景科学结果。DS-50在UAR中显示39Ar降低了1400。在感兴趣区域，电子反冲(ER)背景被完全抑制，分辨率优于1/1.5×10^7。这些结果证明了大型Lar TPC在“仪器背景无模式”下工作的能力--在该模式下，对于DS-20k的计划曝光，在感兴趣区域预期不到0.1个事件(不包括大气和扩散超新星背景中微子的弹性散射的实际核反冲)。DS-20K将具有超低背景，具有现场测量其背景的能力，以及对1TeV/c2(10TeV/c2)质量的WIMP-核子截面1.2 x 10^-47 cm2(1.1 x 10^-46 cm2)的灵敏度，将在100 Tyr的5年运行中实现。该奖项反映了NSF的法定使命，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。