Precision Measurements and Fundamental Symmetries

这项由该奖项支持的研究将测试精确的标准模型预测，并可以通过以下方式提供新物理的固体信号：1)测量Muon的磁性特征，这是费米国家加速器实验室大量产生的一种奇异的基本粒子；2)研究中子在衰变时的详细行为。这项工作解决了我们能问的最深层次的问题：物质是由什么组成的，它是如何形成的，它是如何相互作用的。同时，本工作通过突破磁场测量的极限，满足了两个实验的技术要求。这些技术的许多潜在的额外应用可能扩展到生物学、神经科学和医学。这项研究为密歇根大学的研究生和本科生提供了具有挑战性的研究项目。一批不同的研究生正在研究这项研究的各个方面，他们将加入以前的学生的行列，作为教师、物理和生物医学领域的研究人员以及工业领袖为国家利益做出贡献。这项研究包括推进两项精密测量：Muon磁矩异常g-2和中子衰变中的β-中微子不对称参数。它们解决了基本粒子和核物理中最深层次的问题，即标准模型之外的问题，通过对对新物理最敏感的系统中的测试进行准确的预测。密歇根大学的这个团队正在为Fermilab Muon g-2实验做出贡献，该实验正在完成第一次生产数据运行，目标是通过更好地控制和理解系统误差，达到与先前测量的实验精度相等的水平，并为即将到来的数据运行做准备，目标是将实验精度提高四倍。更具体地说，该小组在精确测量磁场及其绝对校准方面开发了关键创新，并在现场测量数据分析最具挑战性的方面进行了创新，即在校准运行之间进行内插，以跟踪磁场及其空间变化的变化。该小组还将完成调试并开始NAB，这是一种对中子衰变中的β-中微子不对称参数a的新的精确测量，它还通过冗余测量参数lambda来探索标准模型以外的物理，该参数是轴向矢量与矢量耦合常数的比率，也由β不对称性(A)决定。密歇根大学设计和建造的中子自旋翻转装置已经被转移到ORNL国家气象局的基础中子物理束(FNPB)。这将用于确定剩余的中子束极化，这将对测量进行重大的系统校正。由该小组开发和建造的用于绝对校准的He-3磁强计已经完全投入使用，灵敏度为百万分之几(Ppb)，并将潜在地影响从地质学到医学到物理学的精确磁场测量。这项研究将继续提供一些扩展机会，包括关于物理及其应用的公开讲座，本科课程开发，为专业学生提供的讲座，如国家核物理暑期学校。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The research supported by this award will test precise Standard Model predictions and can provide solid signals of new physics by 1) measuring the magnetic signature of the muon, an exotic elementary particle that is produced in abundance at the Fermi National Accelerator Laboratory and 2) studying the detailed behavior of neutrons as they decay. This work addresses the deepest questions that we can ask: what is matter made of, how did it come to be, and how does it interact. At the same time this work addresses the technical demands of the two experiments by pushing the limits of magnetic field measurements. Many potential additional applications of these techniques may be extended into biology, neuroscience and medicine. This research provides challenging research projects for graduate and undergraduate students at the University of Michigan. A diverse cohort of graduate students are working on aspects of this research and will join former students in contributing to the National interest as teachers, researchers in physics and biomedical fields and leaders in industry.This research consists of advancing two precision measurements: the muon magnetic moment anomaly g - 2 and the beta-neutrino asymmetry parameter in neutron decay. These address the deepest question in elementary particle and nuclear physics, namely what lies beyond the Standard Model, by putting precise predictions to the test in systems most sensitive to new physics. This University of Michigan group is contributing to the Fermilab Muon g-2 experiment, which is completing the first production data run with the goal of equaling the experimental precision of the previous measurement with much better control and understanding of the systematic errors, and preparing for the upcoming data runs with the goal of improving the experimental precision by a factor of four. More specifically, the group has developed critical innovations for precision measurement of the magnetic field and its absolute calibration, and innovations in the most challenging aspect of the analysis of the field-measurement data, namely interpolating between calibration runs to track changes in the magnetic field and its spatial variations. The group will also complete commissioning and begin Nab, a new precision measurement of the beta-neutrino asymmetry parameter a in neutron decay that also probes physics Beyond the Standard Model by way of redundantly measuring the parameter lambda, the ratio of axial vector to vector coupling constants, which is also determined by the beta asymmetry (A). The neutron spin flipper designed and built at Michigan has been moved to the Fundamental Neutron Physics Beam (FNPB) at the SNS at ORNL. This will be used in determining the residual neutron beam polarization that would present a major systematic correction to the measurements. The He-3 magnetometer for absolute calibration developed and built by this group is fully operational, has sensitivity of sub ppb (part-per-billion) and will potentially impact precision magnetic field measurements from geology to medicine to physics. This research will continue to seed a number of outreach opportunities including public lectures on physics and its applications, undergraduate course development, lectures for specialist students such as the National Nuclear Physics Summer schools.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.