Neutrino-less Double-Beta Decay with CUORE and the MAJORANA DEMONSTRATOR

这笔拨款部分支持南卡罗莱纳大学（USC）的中微子研究。该小组研究中微子的特性，中微子是宇宙中最多产的粒子，但仍有许多未知之处。主要的努力是寻找假设的，但尚未发现的，被称为零中微子双β衰变的核放射性衰变。这种放射性衰变模式的存在具有重要的后果。它的存在要求中微子有质量，而且中微子本身就是反粒子。最重要的是，这个过程需要违反基本粒子物理学的一个重要的基本守恒定律。南加州大学的研究小组在该领域的两个主要实验中发挥了领导作用：南达科他州桑福德地下研究设施的马约拉纳演示者，以及意大利国家实验室格兰萨索（LNGS）的低温地下观测站（CUORE）。从超低背景探测器所需材料的放射性纯度衍生出来的技术已经直接过渡到国土安全部。来自该项目的四名南加州大学博士生在国土安全部、西北太平洋和萨凡纳河国家实验室担任重要职务。CUORE是一个由988个氧化碲单晶测热计组成的阵列，工作在~8-10 mK，用于寻找碲-130 （Te-130）的零中微子衰变；探测器将包含200公斤Te-130。预测的半衰期灵敏度为~10^（26）年，达到反向层次中微子-质量区域。南加州大学领导部分研发人员确定将Te-130中的CUORE从33.4%富集到93%的可行性和成本，并为辐射热计配备切伦科夫光探测器，以区分α粒子背景。这些升级旨在达到覆盖反向中微子质量层次所需的灵敏度。USC领导CUORE数据分析，通过检测两个电子和级联伽马射线的重合事件，寻找Te-130的零中微子双β衰变到氙-130的第一个激发态0+。该技术在CUORICINO原型实验中实现了零背景。最后，USC集团负责CUORE前端电子设备的生产，并将参与其安装、调试和维护。

This grant partially supports neutrino research at the University of South Carolina (USC). The group studies the properties of the neutrino, the most prolific particle in the universe, about which much is still unknown. The primary effort is the search for the hypothesized, but not yet discovered, nuclear-radioactive decay called zero-neutrino double-beta decay. The existence of such a radioactive decay mode has important consequences. Its existence requires that neutrinos have mass, and that they are their own anti-particles. Most importantly, this process would require the violation of an important fundamental conservation law of elementary particle physics. The USC group has leadership roles in two of the leading experiments in this field: the MAJORANA DEMONSTRATOR, in the Sanford Underground Research Facility in South Dakota, and the Cryogenic Underground Observatory (CUORE) in the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. The spin-off technology from the required radiopurity of materials for the ultra-low background detectors has transitioned directly into Homeland Security. Four past USC PhD students from the program hold important positions in Homeland Security, at the Pacific Northwest and Savannah River National Laboratories. CUORE, nearing completion in the LNGS, is an array of 988 tellurium oxide single-crystal bolometers that operate at ~8-10 mK to search for the zero-neutrino decay of tellurium-130 (Te-130); the detector will contain 200-kg of Te-130. The predicted half-life sensitivity is ~10^(26) years, to reach into the inverted hierarchy neutrino-mass region. USC leads part of the R&D to determine the feasibility and cost of enriching CUORE to 93% in Te-130 from 33.4%, and equipping the bolometers with Cherenkov-light detectors to discriminate against alpha-particle background. These upgrades are designed to reach the sensitivity required to cover the inverted neutrino mass hierarchy. USC leads the CUORE data analysis to search for zero-neutrino double-beta decay of Te-130 to the first excited 0+ state in xenon-130, by detecting the coincidence events from the two electrons and cascade gamma rays. This technique achieved zero-background in the prototype experiment, CUORICINO. Finally, the USC group was responsible for the production of the CUORE front-end electronics, and will participate in its installation, commissioning and maintenance.