Collaborative Research: Combating Cosmogenic Argon Isotopes in LEGEND

合作研究：对抗《LEGEND》中的宇宙成因氩同位素

• 批准号: 2111176
• 负责人: Matthew Green
• 金额: $ 51万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2111176&HistoricalAwards=false
• 关键词: Collaborative; Research; Combating; Cosmogenic; Argon

Neutrinos are electrically neutral and have non-zero mass, although their mass is very small. These properties raise the possibility that neutrinos are their own antiparticles (i.e. Majorana particles). If a neutrino is, indeed, its own anti-particle then this would shed light on the reason why matter dominates over antimatter in our universe and would point to new physics at energies far beyond those of our largest collider-accelerators. If neutrinos are Majorana particles, then double-beta decay without the simultaneous emission of neutrinos, or zero-neutrino double-beta decay (0νββ), becomes possible. The PI will search for 0νββ in an upcoming experiment. The ultra-rare nature of the decay, and the extreme sensitivity sought by the experiment, require backgrounds to be strictly controlled. For example, the experiment must be constructed with ultra-pure materials, be deployed underground, and make use of advanced techniques to discriminate signal from background.The LEGEND experiment will use germanium detectors enriched in the isotope Ge-76 to conduct a search for 0νββ. LEGEND hopes to achieve 10 ton-years of exposure with backgrounds reduced by over an order-of-magnitude compared to what has been previously demonstrated. This project aims to address the leading background contribution to the LEGEND experiment. For example, the presence of trace amounts of radioactive Ar-42 in the liquid argon bath in which LEGEND’s Ge detectors will operate will interfere with the counting of real 0νββ events. The PI will perform measurements in liquid argon in order to develop tools to accurately estimate the impact of this source of background and also develop analysis tools to remove it from the data. The PI also aims to develop a robust and validated background model that can be integrated into the LEGEND data processing framework. The goal is to produce reliable energy spectra which can be used for background estimation and fitting, and accurately model pulse shape discrimination techniques which can be used to suppress backgrounds arising from Ar-42.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.

中微子是电中性的，质量非零，尽管它们的质量非常小。这些性质提高了中微子本身就是反粒子（即马约拉纳粒子）的可能性。如果中微子确实是它自己的反粒子，那么这将阐明为什么物质在我们的宇宙中占主导地位，而不是反物质，并将指出能量远远超过我们最大的对撞机加速器的新物理学。如果中微子是马约拉纳粒子，那么双β衰变而不同时发射中微子，或者零中微子双β衰变（0νββ）就成为可能。PI将在即将到来的实验中寻找0νββ。衰变的超罕见性质，以及实验所追求的极端灵敏度，需要严格控制背景。例如，实验必须用超纯材料建造，部署在地下，并使用先进的技术来区分信号和背景。LEGEND实验将使用富含同位素Ge-76的锗探测器来寻找0νββ。LEGEND希望达到10吨年的曝光量，背景比之前演示的要减少一个数量级以上。本项目旨在解决LEGEND实验的主要背景贡献。例如，在LEGEND的Ge探测器将运行的液态氩浴中存在痕量的放射性Ar-42，这将干扰对真实的0νββ事件的计数。PI将在液态氩气中进行测量，以便开发工具来准确估计该背景源的影响，并开发分析工具来从数据中删除它。PI还旨在开发一个可集成到LEGEND数据处理框架中的强大且经过验证的背景模型。目标是产生可用于背景估计和拟合的可靠能量谱，并准确地模拟可用于抑制Ar-42产生的背景的脉冲形状识别技术。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。