Determination of the electron neutrino rest mass via tritium decay

通过氚衰变测定电子中微子静止质量

• 批准号: 0104100
• 负责人: Manfred Fink
• 金额: $ 31.62万
• 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: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2005-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0104100&HistoricalAwards=false
• 关键词: Determination; electron; neutrino; rest; mass

The experimental determination of the mass of the neutrinos (orantineutrinos) is a slow and increasingly more complex process. The electron antineutrinos are the favored object. They are produced during beta-decay, and electrons are ejected at the same time. Their properties link directly to the spin and mass of the escaping neutrino through fundamental conservation laws. The preferred beta decay source is tritium since the electrons have only 18.56 KeV energy at the endpoint of the beta spectrum. This is a value, which is technologically achievable even with meV resolution. However one is dealing with the endpoint of the beta spectrum, where the intensities of the electron fluxes per eV energy interval are down by 10 order of magnitudes. This is the quintessential problem for all experiments aimed at the direct determination of the neutrino mass. All neutrino rest mass experiments must include electron spectrometers with high resolution; ultralow dark count detectors, excellent calibration procedures, and superstabilities for all experimental parameters to collect data for very long times to cope with the statistical uncertainties. A new effort is under way at the Physics Department of The University of Texas at Austin, in cooperation with the University of Nebraska, Brandeis University, Michigan Tech University, PomonaCollege, and The University of Texas at Arlington. Our approach is based on a series of electrostatic electron analyzers, which are designed to record the beta electron energies with about 1 eV resolution. The source is gaseous, molecular tritium at 30K. The detectors are easily accessible and can be shielded from unwanted cosmic radiation to 1 dark count per day. There is no magnetic field inside the whole apparatus. Furthermore we will use the gas cell as a target for electron diffraction in order to calibrate the voltages at the spectrometers with the de Broglie wavelenghts of electrons produced by a telefocus electron gun. This is possible since the bond length of T2 is very well known from Raman spectroscopy. The beam electrons will also give us laso the spectrometer function to about .2 eV resolution. In summary, when all units work as designed our experiment will lead to a determination of the mass of the elctron antineutrino at the .5 eV level.

中微子（Orantineutrinos）质量的实验确定是一个缓慢且越来越复杂的过程。电子抗腐殖质是最受欢迎的物体。它们是在Beta-Decay期间生产的，并且电子被同时弹出。它们的性质通过基本的保护法直接与逃脱中微子的自旋和质量联系起来。首选的β衰变源是tri tritium，因为电子在β频谱的端点上只有18.56 keV能量。这是一个价值，即使是MEV解决方案，在技术上也可以实现。但是，一个人正在处理β频谱的终点，其中每个EV能量间隔的电子通量的强度下降了10个幅度。这是所有旨在直接确定中微子质量的实验的典型问题。所有中微子休息质量实验必须包括具有高分辨率的电子光谱仪；超大的深色计数检测器，出色的校准程序和所有实验参数的超级震撼力，以收集很长时间的数据，以应对统计不确定性。 德克萨斯大学奥斯汀分校的物理系正在与内布拉斯加州大学，布兰代斯大学，密歇根理工大学，波莫纳科洛格和德克萨斯大学阿灵顿分校合作。我们的方法基于一系列静电电子分析仪，这些静电电子分析仪旨在记录约1 eV分辨率的β电子能。源是气态，分子tri tri tritium在30k处。探测器很容易访问，可以从不需要的宇宙辐射屏蔽到每天1个黑暗计数。 整个设备内部没有磁场。此外，我们将使用燃气电池作为电子衍射的目标，以便用电focus电子枪产生的电子的de broglie wavelenghts在光谱仪处校准电压。这是可能的，因为T2的键长可以从拉曼光谱中众所周知。梁电子还将使我们的LASO频谱仪函数约为.2 EV分辨率。 总而言之，当所有单元按设计工作时，我们的实验将导致确定.5 eV水平的Elctron antineutrino的质量。