Search for Neutrinoless Double Beta Decay with the NEMO-3 and SuperNEMO Experiments

通过 NEMO-3 和 SuperNEMO 实验寻找无中微子双贝塔衰变

• 批准号: 1505149
• 负责人: Karol Lang
• 金额: $ 45万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505149&HistoricalAwards=false
• 关键词: Search; Neutrinoless; Double; Beta; Decay

Neutrinos are some of the most intriguing elementary particles that make up the Standard Model of particle physics. They were long thought to have no mass, don?t interact with much of anything, and may hold the key to why there is more matter than antimatter in the Universe. Neutrinos are commonly observed in beta decay, a radioactive process that involves the emission of an electron (or its antiparticle the positron) from the nucleus, and which is always accompanied by the emission of a neutrino (or its antiparticle the antineutrino) as well. This research focuses on the search for what is called neutrino-less double beta decay, where an initial nucleus with atomic weight and number (A,Z) is transformed into a nucleus of (A, Z + 2) with the emission of only two electrons and nothing else. According to the Standard Model of particle physics, this can only happen if neutrinos and antineutrinos are exactly the same, that is, the neutrino is its own antiparticle. It is believed that this overlap between matter and antimatter could prove essential in answering one of the most fundamental questions in science: why is our Universe made exclusively of matter? The research uses the NEMO-3 and SuperNEMO experiments. The NEMO-3 experiment employed thin foils of particular nuclear isotopes surrounded by detectors that could provide 3D particle tracking of the decay electrons. This unique technique provides several observables for each registered event, offering a powerful means to identify double beta decays and to reject background processes. SuperNEMO will further exploit the NEMO-3 technique. The research group supported by this award will continue its participation in the NEMO-3 data analysis and in the construction of the first SuperNEMO module ("Demonstrator"). Through their activities, the group will educate and train young researchers in building state-of-the-art research instruments and science projects. They will work towards building on the University of Texas at Austin campus an exhibit gallery illustrating the discovery, the underlying physics, and applications of natural radioactivity, cosmic rays, and related subatomic phenomena. The NEMO-3 analysis has already yielded high precision measurements of double beta half-lives for seven isotopes and set some of the most stringent constraints on the neutrino-less transitions, yielding an upper limit for the effective neutrino mass of (0.3-0.9)eV, where the span reflects uncertainties in the nuclear matrix element. The SuperNEMO aspects include designing and fabrication of the central source foil frame, the light injection and calorimeter monitoring system, and the Bi-207 calibration deployment. For the next three years, a critical period for completing and commissioning the Demonstrator, the group will complete hardware commitments and will participate in analysis of data from the new experiment.

中微子是构成粒子物理学标准模型的最有趣的基本粒子之一。 它们一直被认为没有质量，唐？它不与任何东西相互作用，可能是宇宙中物质多于反物质的关键。 中微子通常在β衰变中观察到，β衰变是一种放射性过程，涉及从原子核发射电子（或其反粒子正电子），并且总是伴随着中微子（或其反粒子反中微子）的发射。 这项研究的重点是寻找所谓的无中微子双β衰变，其中原子量和原子数为（A，Z）的初始原子核转化为（A，Z + 2）的原子核，只有两个电子发射，没有其他电子。 根据粒子物理学的标准模型，这只有在中微子和反中微子完全相同的情况下才会发生，也就是说，中微子是它自己的反粒子。 人们相信，物质和反物质之间的这种重叠可以证明在回答科学中最基本的问题之一时是必不可少的：为什么我们的宇宙完全由物质组成？ 该研究使用NEMO-3和SuperNEMO实验。 NEMO-3实验使用了特定核同位素的薄箔，周围环绕着探测器，可以提供衰变电子的3D粒子跟踪。这种独特的技术为每个注册的事件提供了多个可观察值，提供了识别双β衰变并拒绝后台过程的强大方法。SuperNEMO将进一步利用NEMO-3技术。该奖项支持的研究小组将继续参与NEMO-3数据分析和第一个SuperNEMO模块（“演示器”）的建设。通过他们的活动，该小组将教育和培训年轻研究人员建立最先进的研究仪器和科学项目。他们将致力于在德克萨斯大学奥斯汀分校建立一个展览馆，展示自然放射性、宇宙射线和相关亚原子现象的发现、基本物理学和应用。NEMO-3分析已经对七种同位素的双β半衰期进行了高精度测量，并对中微子-少跃迁设置了一些最严格的限制，产生了有效中微子质量的上限（0.3-0.9）eV，其中跨度反映了核矩阵元素的不确定性。SuperNEMO方面包括设计和制造中心源箔框架、光注入和量热计监测系统以及Bi-207校准部署。在接下来的三年里，这是完成和调试演示器的关键时期，该小组将完成硬件承诺，并将参与新实验的数据分析。