Neutrino-Less Double Beta Decay with EXO-200 and EXO

该奖项为该小组继续参与富集氙天文台（EXO）计划提供了基础支持，该计划旨在寻找136-氙中不含中微子的双β衰变，这一核过程可能为了解中微子的本质提供线索。对这种衰变的观察意味着中微子是马约拉纳粒子，即它们自己的反粒子，这对我们理解基本粒子的质量模式以及早期宇宙的结构和演化具有深远的意义。EXO-200实验是一个200公斤的浓缩液体氙探测器，目前正在新墨西哥州的废物隔离试验工厂（WIPP）的地下运行。该小组还将参与EXO-200之后更灵敏的吨级EXO实验（全EXO）的开发和设计。在马萨诸塞大学的计划研究中，该小组将为设计一个对中微子质量灵敏度低至10 meV的全exo实验提供关键输入：i)优化探测器的光学响应和VUV探测效率，ii)提供单个钡离子源，这可能是实现exo特定背景抑制方案的一个改变游戏的工具，该方案寻找钡离子在136-Xe双β衰变后的外观。更广泛的影响：惰性液体探测器正在医学成像设备以及核电站燃料成分的远程监测中得到应用。为像EXO-200这样的探测器开发的超低本底方法已经将放射性污染降低到了20年前被认为不可能达到的水平。现在，电子工业感兴趣的工艺要求其生产线上的放射性纯度达到类似水平。与EXO-200和EXO的合作为研究生提供了充分的机会，可以在中型国际科学合作中进行前沿研究和工作经验。

This award provides base support for the group to continue to participate in the Enriched Xenon Observatory (EXO) program to search for neutrino-less double beta decay in 136-Xenon, a nuclear process which could hold clues into the nature of neutrinos. Observation of this decay would imply that neutrinos are Majorana particles, i.e. their own antiparticles, with profound implications on our understanding of the pattern of masses of fundamental particles and of the structure and evolution of the early universe. The EXO-200 experiment, a 200-kg enriched liquid xenon detector is now running underground at the Waste Isolation Pilot Plant (WIPP) in New Mexico. This group will also take part in the development and design of a more sensitive tonne-scale EXO experiment (full-EXO) to follow EXO-200. With the planned research at UMass, the group will provide key input to the design of a full-EXO experiment with sensitivity to neutrino masses as small as 10 meV by: i) optimizing the optical response and VUV detection efficiency of the detector, and ii) supplying a single Barium ion source, a possibly game-changing tool for the realization of the EXO-specific background suppression scheme which looks for the appearance of Barium ions following 136-Xe double beta decay.Broader Impacts: Noble liquid detectors are finding applications in medical imaging devices as well as in remote monitoring of nuclear power plant fuel composition. The ultra-low background methods developed for detectors like EXO-200 have taken radioactive contamination to levels considered impossible to achieve just twenty years ago. Processes of interest for the electronics industry now require similar levels of radio-purity in their manufacturing lines. Work with EXO-200 and EXO provides ample opportunities for graduate students to perform cutting edge research and experience working in a medium-sized international scientific collaboration.