Barium Daughter Tagging for the nEXO Double Beta Decay Experiment

这个项目旨在开发一种基于激光的精确测量技术，它将能够在一个装有5吨液态氙的容器中探测到单个钡原子。这样做将使核物理学家能够有效地进行正在进行的实验，否则将需要几倍大的设备。核物理学家正在寻找自然界中一种极其罕见的放射性衰变，这种衰变已被理论化，但尚未被发现。这种将一个氙原子变成一个钡原子的衰变的发现，将首次证明自然界中最小的弱相互作用粒子之一——中微子，与它们的反粒子——反中微子是一样的。证明物质的一个组成部分与其对应的反物质是相同的，可能有助于理解为什么我们的宇宙只由物质组成，而反物质的数量可以忽略不计，而宇宙大爆炸理论预测物质和反物质的初始形成是等量的。在这个项目中，一个合适颜色的激光被扫描穿过一个样品，样品中含有一些钡原子或离子，这些钡原子或离子被捕获在冷冻固体的氙中，每次激光击中一个原子或离子，就会记录下一个特有的闪光。从事这项研究的科学家们最近首次证明，被困在固体稀有元素中的单个原子可以在背景下以高选择性成像和计数。该项目将固体氙基质中两个特定位置或相邻配置的单个钡原子的成像和计数扩展到所有重要基质位置的钡原子和离子。在氙中微子双β衰变探测器中，有必要从液态氙体积中抓取和计数固体氙中的单个子钡原子或离子。工作的第二个重点是在一个小的液态氙测试室中演示和完善这种钡捕获和计数能力。拟议的研究基本上是跨学科的，并有望取得广泛的科学兴趣。它涉及将最初在原子，分子和光学物理框架内开发的单原子检测技术应用于浓缩惰性气体环境中的原子，同时提供核物理学的转型进步。该项目有一个教育和推广部分，将高中教师与最先进的研究联系起来。该项目由三个NSF项目（实验原子、分子和光学物理；实验核物理，都在物理部；化学测量和成像，在化学部）共同资助。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。

This project aims to develop a laser-based measurement technique so precise that it will be able to detect a single atom of barium in a tank of five tons of liquid xenon. Doing so will enable nuclear physicists to efficiently carry out an ongoing experiment that would otherwise require a device that is several times larger. The nuclear physicists are searching for an extremely rare radioactive decay in nature that has been theorized but has not yet been found. The discovery of this decay, which changes one xenon atom into one barium atom, would prove for the first time that one of the smallest and weakly interacting particles in nature, neutrinos, are the same as their anti-particles, the antineutrinos. The proof that a component of matter is the same as its antimatter counterpart could contribute to an understanding of why our universe is composed of matter only, with negligible amounts of antimatter, whereas Big Bang theories of the universe predict initial formation of equal parts of matter and antimatter. In this project a laser of the right color is scanned across a sample containing a few barium atoms or ions captured in xenon that is frozen solid, and each time the laser hits an atom or ion, a characteristic flash of light is recorded.The scientists doing this research have recently demonstrated for the first time that individual atoms trapped in a solid noble element can be imaged and counted with high selectivity against background. This project extends the imaging and counting of individual barium atoms in two particular sites, or configuration of neighbors, in a solid xenon matrix to both barium atoms and ions in all the significant matrix sites. In a xenon neutrinoless double beta decay detector, it will be necessary to grab and count individual daughter barium atoms or ions in solid xenon from the liquid xenon volume. A second focus of the work is to demonstrate and perfect this barium capture and counting capability in a small liquid xenon test chamber. The proposed research is fundamentally interdisciplinary and promises advances of broad scientific interest. It involves applying single atom detection techniques originally developed within the framework of Atomic, Molecular and Optical physics to atoms in a condensed noble gas environment, while offering a transformational advance in nuclear physics. The project has an educational and outreach component to connect high school teachers to state-of-the-art research. The project is jointly funded by three NSF Programs (Experimental Atomic, Molecular, and Optical Physics; Experimental Nuclear Physics, both in the Physics Division; and Chemical Measurement and Imaging, in the Chemistry Division).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.