Barium Daughter Tagging for the nEXO Double Beta Decay Experiment

该项目旨在开发一种基于激光的测量技术，该技术非常精确，能够在一个5吨液体氙气的水箱中检测到一个单一的钡原子。这样做将使核物理学家能够有效地进行正在进行的实验，否则需要几倍大的设备。核物理学家们正在寻找自然界中一种极其罕见的放射性衰变，这种衰变已经形成了理论，但尚未被发现。这种衰变会把一个氙气原子变成一个钡原子，这种衰变的发现将首次证明自然界中最小、相互作用最弱的粒子之一中微子与它们的反粒子反中微子是一样的。物质组分与反物质组分相同的证据可能有助于理解为什么我们的宇宙只由物质组成，反物质的量可以忽略不计，而宇宙大爆炸理论预测物质和反物质的初始形成部分相等。在这个项目中，用合适颜色的激光扫描一个样本，其中包含一些被冷冻的氙气捕获的钡原子或离子，每次激光击中原子或离子时，都会记录下一道特有的闪光。进行这项研究的科学家最近首次证明，可以对被困在固体贵重元素中的单个原子进行成像，并对背景进行高选择性的计数。该项目将固体氙气基质中两个特定位置的单个钡原子或相邻原子的组态的成像和计数扩展到所有重要基质位置的钡原子和离子。在无氙气中微子双β衰变探测器中，需要从液态氙气体积中抓取和计数固体氙气中的单个子体钡原子或离子。这项工作的第二个重点是在一个小的液体氙气试验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，并有望取得具有广泛科学兴趣的进展。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探测技术应用于凝聚惰性气体环境中的原子，同时在核物理方面取得革命性进展。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NSF的三个项目(物理部的实验原子、分子和光学物理；物理部的实验核物理；化学部的化学测量和成像)联合资助。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。

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.