Collaborative Research: Combating Cosmogenic Argon Isotopes in LEGEND

中微子是电中性的，质量不为零，尽管它们的质量很小。这些性质增加了中微子是它们自己的反粒子(即Majorana粒子)的可能性。如果中微子确实是它自己的反粒子，那么这将有助于解释为什么物质在我们的宇宙中主导着反物质，并将指向能量远远超过我们最大的对撞机-加速器的新物理。如果中微子是马约拉纳粒子，那么在没有中微子同时发射的情况下，双贝塔衰变或零中微子双贝塔衰变(0νββ)成为可能。PI将在即将到来的实验中搜索0νββ。衰变的极端稀有性质，以及实验所寻求的极端敏感性，要求严格控制背景。例如，该实验必须用超纯材料建造，部署在地下，并利用先进的技术区分信号和背景。传奇实验将使用富含同位素Ge-76的锗探测器进行0νββ的搜索。联想希望实现10吨年的曝光量，背景比之前展示的减少了一个数量级以上。这个项目旨在解决对传奇实验的主要背景贡献。例如，在联想的Ge探测器将在其中运行的液态Ar-42中存在微量放射性Ar-42，将干扰对真实0νββ事件的计数。PI将在液态Ar中进行测量，以便开发工具来准确估计这一背景来源的影响，并开发分析工具将其从数据中删除。PI还旨在开发一个健壮且经过验证的背景模型，该模型可集成到图例数据处理框架中。目标是产生可靠的能谱，可用于背景估计和拟合，并准确地模拟脉冲形状识别技术，可用于抑制Ar-42产生的背景。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。

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.