INSPIRE: Development of a Technique to Detect Single Ba Atoms in Solid Xe Matrix Toward Be Tagging in nEXO

该INSPIRE项目由物理系的实验核物理和原子、分子和光学物理方案，化学系的化学测量和成像方案（这两个部门都属于NSF的数学和物理科学理事会）以及综合活动办公室共同资助。该奖项支持使用激光光谱学的新方法发现和开发一种技术，以检测和独特地识别五吨液体氙中的一个钡原子。 最终的目标是发现一种罕见的放射性衰变，称为无中微子双β衰变，即同位素136 π。 所提出的单钡检测技术将使这种衰变的实验搜索显着更灵敏。 这种衰变的发现将表明中微子与反中微子是一样的。 这将从根本上改变我们对物质基本成分的看法，并可能有助于理解为什么宇宙中的物质比反物质多。 本计画所发展之仪器与方法可能与化学中所使用之基质分离实验有关。 拟议的工作也有非常重要的教育和推广组成部分，因为它连接高中教师的最先进的研究。 在单原子水平上探测固体氙中钡原子的研究最近取得了重大突破。将支持持续的跨学科研究，其中Ba的单个原子将通过激光诱导荧光成像，同时被困在首先在蓝宝石窗口上生长的固体晶体基质中，然后在光学可访问探针上结束。 还计划在液体氙探针上捕获和检测Ba原子的研究。 这项工作的最终目标是捕获和探测136 Ba无中微子双β衰变的单个136 Ba子体，推进可能是吨级实验的最终背景抑制方法。这种技术提供的可能性是136中微子独有的，再加上nEXO探测器的第二阶段，可以大大提高其灵敏度，超过10^28年的半衰期，允许探索中微子质量的部分正常等级制度。 无中微子双β衰变的观测回答了核物理学中的一个重大挑战，即自然界中是否存在双组分马约拉纳费米子。 这可能会对中微子具有有限的质量，但它们比所有其他已知粒子轻得多这一令人困惑的事实有所启发。此外，无中微子双β衰变的观测将提供中微子质量尺度的测量，并证明轻子数违反的第一个案例。

This INSPIRE project is jointly funded by the Experimental Nuclear Physics and the Atomic, Molecular and Optical Physics programs in the Physics Division, the Chemical Measurement and Imaging program in the Chemistry Division (both Divisions are in the Mathematical and Physical Sciences Directorate of NSF), and the Office of Integrative Activities. The award supports the discovery and development of a technique to detect and uniquely identify one barium atom in five tons of liquid xenon using novel methods of laser spectroscopy. The ultimate goal is the discovery of a rare radioactive decay, called neutrinoless double-beta decay, of the isotope 136Xe. The proposed single-Ba detection technique would make the experimental search for this decay significantly more sensitive. A discovery of this decay would show that neutrinos are the same as anti-neutrinos. This would fundamentally change our view of the elementary components of matter and would potentially contribute to an understanding of why there is more matter than anti-matter in the universe. Instruments and methods developed in this project may be relevant to the kinds of matrix isolation experiments used in chemistry. The proposed work also has very important educational and outreach components, as it connects high school teachers to state-of-the-art research. A major breakthrough in detecting barium atoms in solid xenon at the single atom level has recently been achieved. Continued interdisciplinary research will be supported in which individual atoms of Ba will be imaged by laser-induced fluorescence while trapped in a matrix of solid Xe grown first on a sapphire window and then at the end on an optically accessible probe. Research on grabbing and detecting Ba atoms on a probe from liquid xenon is also planned. The ultimate goal of the work is to capture and detect a single 136Ba daughter of neutrinoless double-beta decay of 136Xe, advancing what may be the ultimate background suppression method for ton-scale experiments. The possibility afforded by this technique is unique to 136Xe and, coupled to a second phase of the nEXO detector, could substantially improve its sensitivity beyond 10^28 year half life, allowing the exploration of part of the normal hierarchy regime of neutrino mass. The observation of neutrinoless double-beta decay answers a grand challenge in nuclear physics, whether or not 2-component Majorana fermions exist in Nature. This may shed some light on the puzzling fact that neutrinos have a finite mass and yet they are so much lighter than all other known particles. In addition the observation of neutrinoless double-beta decay would provide a measurement of the neutrino mass scale and demonstrate the first case of lepton number violation.