Determination of the mass of the Electron anti-neutrino via beta decay

NEXTEX是美国德克萨斯州的中微子质量实验项目，该项目旨在通过观察氚分子β衰变谱的终点来确定电子中微子的质量。 目前这种技术对中微子质量的限制约为2 eV/c2，但这一结果似乎受到系统不确定性的影响。 预计质量至少比这个值小一个数量级，可能在0.2 eV/c2左右。NEXTEX建议使用β衰变中产生的电子的纯静电分析来进行这种终点观察，这与之前的测量和KATRIN不同，KATRIN预计将提供准确性的下一个主要步骤，所有这些都利用了β衰变产生的电子的磁性分析。 NEXTEX装置的附加特征包括使用电子枪，以通过观察在其检测器位置处产生的电子衍射图案来将装置校准到优于1 eV。 建议的NEXTEX的精度优于0.8 eV/c2的电子中微子的质量。 因此，预计NEXTEX无法达到KATRIN的精度，KATRIN的精度设计为0.2 eV/c2。 然而，NEXTEX很可能比KATRIN更快地产生测量结果，并且它可能产生系统不确定性的重要识别，这些不确定性在测量结果扩展到低于目前的精度水平之前很难预测。NEXTEX是6所大学的合作项目，由德克萨斯大学的小组领导。 因此，它涉及到几个研究生在其努力。 它更广泛的影响当然包括它对基础物理学的影响，因为它为直接测量得到的电子中微子的质量提供了一个新的极限。

Summary of NEXTEX, the Neutrino mass EXperiment at TEXasThis project is designed to determine the mass of the electron neutrino from observation of the end point of the beta-decay spectrum of molecular tritium. The current limit on neutrino mass from this technique is around 2 eV/c2, but this result appears to be dominated by systematic uncertainties. The mass is expected to be at least an order of magnitude less than this value, possibly around 0.2 eV/c2. NEXTEX proposes to make this end point observation using purely electrostatic analysis of the electrons produced in the beta decays, unlike the previous measurements and KATRIN, the experiment that is expected to provide the next major step in accuracy, all of which utilized magnetic analysis of the electrons resulting from the beta decay. Additional features of the NEXTEX apparatus include use of an electron gun to calibrate the apparatus to better than 1 eV via observation of the electron diffraction pattern produced at its detector location. The proposed accuracy of NEXTEX is better than 0.8 eV/c2 for the mass of the electron neutrino. Thus NEXTEX is not expected to achieve the accuracy of KATRIN, which is designed to provide an accuracy of 0.2 eV/c2. However, NEXTEX may well produce a measurement sooner than can KATRIN, and it may produce important identifications of systematic uncertainties that are difficult to anticipate until the measurements are extended below present levels of accuracy.NEXTEX is a collaboration of 6 universities, and is headed by the group at the University of Texas. Thus it involves several graduate students in its efforts. Its broader impacts certainly include the impact it will have on fundamental physics by providing a new limit on the mass of the electron neutrino as obtained from direct measurement.