A Tonne-Scale Ge Experiment

这项提议将为寻找无中微子双β衰变提供资金。中微子是基本粒子，在早期宇宙学、宇宙学和天体物理学、核物理学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。一个1吨重的探测器搜索中微子较少的双β衰变将比目前的测量灵敏100倍左右，并将确认或排除马约拉纳中微子的反向质量等级。为了最终实现使用Ge探测器的1吨级探测器，Majorana和GERDA合作建立了正式的合作协议。合作双方同意分享探测器设计开发方面的资源和知识，以达到50 meV以下的马约拉纳质量灵敏度。这一建议要求支持1吨规模的锗实验的设计。根据Majorana协作组和GERDA协作组两个不同的概念，将对一个装置进行工程、设计、模拟和风险分析。根据吨级无中微子双β衰变实验开发的更大、更低背景Ge阵列技术，有望实现新一代高效、超低本底伽马能谱测量。将受益于这一新一代技术的领域包括：测量环境中的人为辐射;通过天然同位素示踪剂测量大气、海洋和地下水的环境迁移;放射性定年方法;反应堆监测;确定极低职业辐射照射的生物测定;以及涉及极低放射性示踪剂的生物研究。学生和博士后将接受深层地下物理学和相关学科的培训，如低背景技术，探测器技术，核物理和中微子物理。北卡罗来纳州大学校园内的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.