A Tonne-Scale Ge Experiment

这项提议将为寻找无中微子的双β衰变提供资金。中微子是基本粒子，在早期宇宙、宇宙学和天体物理学、核物理和粒子物理学中发挥着关键作用。中微子振荡实验的结果提供了令人信服的证据，证明中微子具有质量，并首次表明核物理和粒子物理的标准模型是不完整的。寻找不含中微子的双β衰变的1吨探测器将比目前的测量灵敏100倍，并将确认或排除马约拉纳中微子的反向质量层次。为了最终实现使用锗探测器的1吨级探测器，马约拉纳和GERDA合作已经建立了正式的合作协议。双方已同意在开发探测器设计方面共享资源和知识，以达到低于50兆电子伏特的马约拉纳质量灵敏度。本提案要求支持设计1吨规模的Ge实验。工作将基于两个不同的概念，一个由Majorana合作开发，另一个由GERDA合作开发，对设备进行工程、设计、模拟和风险分析。从吨级无中微子双β衰变实验中开发的更大、更低背景的Ge阵列技术有望实现新一代高效、超低背景的伽马能谱测量。从新一代技术中受益的领域包括：环境中人为辐射的测量；通过天然同位素示踪剂测量大气、海洋和地下水环境运输；放射性测年法；反应堆监控;测定极低职业照射量的生物测定法；生物研究涉及放射性示踪剂的低活性。培养深地下物理及相关学科的学生和博士后，如低背景技术、探测器技术、核物理和中微子物理。北卡罗来纳大学莫尔黑德天文馆的一个教育和推广项目将把这门科学带给公众。

This proposal will fund the search for neutrino-less double beta decay. The neutrinos are fundamental particles that play key roles in the early universe, in cosmology and astrophysics, and in nuclear and particle physics. Results from neutrino oscillation experiments have provided compelling evidence that neutrinos have mass and give the first indication that the Standard Model of nuclear and particle physics is incomplete. A 1-tonne detector searching for neutrino-less double beta-decay will be about 100 times more sensitive than current measurements and will confirm or exclude the inverted mass hierarchy for Majorana neutrinos. To achieve the ultimately realizing 1-tonne scale detectors using Ge detectors, the Majorana and GERDA collaborations have established a formal cooperative agreement. The collaborations have agreed to share resources and knowledge in their development of detector designs to reach for a Majorana mass sensitivity below 50 meV. This proposal requests support for the design of a 1-tonne-scale Ge experiment. Work will be performed on the engineering, design, simulation, and risk analysis of an apparatus based on two different concepts, one developed by the Majorana collaboration, and the other by the GERDA collaboration.The technology of larger, lower-background Ge arrays developed from a tonne-scale neutrino-less double beta decay experiment can be expected to enable a new generation of highly efficient, ultra-low-background gamma spectroscopy measurements. Among the fields that stand to benefit from this new generation of technology are: measurements of anthropogenic radiation in the environment; atmospheric, ocean, and groundwater environmental transport measured via natural isotopic tracers; methods of radioactive dating; reactor monitoring; bioassay for determining very low occupational exposures to radiation; and biological studies involving radiotracers at very low activities. Students and postdocs will be trained in deep underground physics and related disciplines, such as low-background techniques, detector technology, nuclear physics and neutrino physics. An education and outreach program with the Morehead Planetarium on the campus of University of North Carolina will bring this science to the public.