Precision Measurements and Fundamental Symmetries

对基本粒子性质进行精确的实验测试，现在是一种行之有效的方法，可以超越我们目前的物理知识，寻找新的自然规律。这项提案中提出的研究挑战了精确的标准模型预测，并可以通过测量μ子的磁矩异常来提供新物理学的可靠信号。μ子是费米国家加速器实验室大量产生的一种已知的基本粒子。提出的研究也是为了研究中子的放射性衰变的详细行为。这项工作解决了最深层次的问题：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，本研究解决了实验的技术需求，将磁场测量的极限推向了更高的水平。标准模型预测与μ子g-2的实验值之间存在3.6西格玛的差异，为新物理提供了持久的实验室信号，我们有机会提高精度并加强信号以达到发现水平。作为费米实验室μ子g-2合作项目的一部分，我们的目标是将实验精度提高四倍，如果中心值不变，将产生7西格玛信号，如果理论误差减小，则会产生更大的信号。密歇根大学的研究小组已经将其工作从具有中子极化和精密中子极化测量专业知识的基础中子物理学转移到介子存储环磁场的测量问题上。在精密自旋进动和基于核磁共振的极化3He磁强计方面的专业知识和经验将应用于磁场测量系统的绝对校准问题和确定现场测量的系统误差。特别是，这项研究将资助：1)核磁共振技术的发展和基于核磁共振的磁场测量系统的系统学；2)彭宁陷阱中3He磁矩的绝对测量。此外，该研究将完成用于Nab实验的SNS光束的开发，特别是使用3He自旋滤波器确定基本中子物理束线（FNPB）光束的剩余极化。

Precise experimental tests of fundamental particle properties are now a well-established way to search for new laws of nature beyond our current physical knowledge. The research presented in this proposal challenges precise Standard Model predictions and could provide solid signals of new physics by measuring the magnetic-moment anomaly of the muon, a known elementary particle that is produced in abundance at the Fermi National Accelerator Laboratory. The proposed research is also to study the detailed behavior of the radioactive decay of neutrons. This work addresses questions at the deepest level: what is matter made of, how did it come to be and how does it interact? At the same time, this research addresses the technical demands of the experiments by pushing the limits of magnetic field measurement to a higher level.The existing 3.6-sigma difference between the Standard-Model prediction and the experimental value of g-2 of the muon provides a persistent laboratory signal of new physics, and we have the opportunity to advance the precision and strengthen the signal to reach discovery level. As part of the Fermilab Muon g-2 collaboration, our goal is to improve the experimental precision by a factor of four, which would result in a 7-sigma signal if the central value does not change, or even larger if the theory error is reduced. The University of Michigan group has shifted its effort from fundamental neutron physics with expertise in neutron polarization and precision neutron polarimetry to the problem of measurement of the muon-storage ring magnetic field. This expertise and experience in precision spin-precession and NMR-based magnetometry with polarized 3He will be applied to the problem of absolute calibration of the magnetic field measurement system and determining the systematic errors on the field measurement. In particular, this research will fund: 1) development of NMR techniques and systematics of the NMR-based magnetic-field measurement system and 2) work towards an absolute measurement of the 3He magnetic moment in a Penning trap. Furthermore, the proposed research will complete the development of the SNS beam for the Nab experiment, specifically the determination of the residual polarization of the Fundamental Neutron Physics Beamline (FNPB) beam using a 3He spin filter.