Precision Measurements with Cold and Ultracold Neutrons

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。研究项目涵盖了几个研究项目，其中使用极低能量中子来加强我们对基本相互作用的理解。在第一个项目中，研究了中子β衰变中的几个可观测量;将这些可观测量与另一个实验结果（中子寿命的测定）相结合，确定了导致中子衰变的弱相互作用的耦合常数。它们被用来作为一个敏感的测试的有效性，目前的理论，描述弱相互作用耦合核子轻子（电子和中微子产生的中子衰变）。一个相关的过程是核子和其他核子之间的弱耦合，和第二个项目，测量的γ射线发射相对于质子上的中子俘获中子的极化方向的不对称性，进行以确定强度的主导过程的核子之间的弱相互作用。第三个项目是超冷中子在玻璃镜引力场中的引力束缚量子态的表征。一系列的实验被用来寻找新的短程相互作用会影响这些量子态。最后，将为氦-4建造一个净化器，氦-4被用作超冷中子的生产目标，以寻找中子的电偶极矩。氦-3污染必须降低到远低于自然丰度，以避免超冷中子对氦-3杂质的重新作用。这个实验计划的共同目标是在以前无法到达的区域测试标准模型，或者至少不那么精确。发现标准模型中没有解释的东西将对高能物理学和宇宙学产生重要影响。此外，这些实验具有很高的教育潜力：除了在科学上可见和技术上具有挑战性的项目上工作的优势外，美国和国际机构的中等规模合作中教授的工作道德对学生来说具有很大的价值，无论是作为未来的科学家还是学术界以外的人。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The research projects covers several research projects in which very low energy neutrons are used to strengthen our understanding of fundamental interactions. In the first project, several observables in neutron beta decay are studied; the combination of these observables with another experimental result (the determination of the neutron lifetime) determines the coupling constants of the weak interaction which causes the neutron decay. They are used as a sensitive test of the validity of the present theory which describes weak interaction coupling nucleons to leptons (the electrons and neutrinos produced in neutron decay). A related process is the weak coupling between nucleons and other nucleons, and the second project, a measurement of the asymmetry in the direction of gamma ray emission relative to the polarization of a neutron in the neutron capture on protons, is performed to determine the strength the dominant process of the weak interaction between nucleons. The third project is the characterization of gravitationally bound quantum states of ultracold neutron in the gravitational field over a glass mirror. A series of experiments is used to search for new short range interactions which would influence these quantum states. Finally, a purifier will be built for Helium-4 which is used as a production target for ultracold neutrons in a search for the electric dipole moment of the neutron. The Helium-3 contamination has to be reduced far below the natural abundance to avoid the reassertion of the ultracold neutrons on Helium-3 impurities.The common goal of this experimental program is to test the Standard Model in regions which were not accessible before, or at least not as precise. A discovery of something not explained in the Standard Model would have important implications for High Energy Physics and Cosmology. Additional, the experiments have a high educational potential: Besides the advantages of working on scientifically visible and technologically challenging projects, the work ethics taught in medium-size collaborations of US and international institutions is of great value to students, be it as future scientist or outside academia.