MRI Consortium: Development of a Room-Temperature Apparatus to Measure the Electric Dipole Moment of the Neutron, for a fast-track ten-fold improvement in sensitivity

该奖项支持在洛斯阿拉莫斯国家实验室（LANL）建立一个新的实验，该实验将在非常小的尺度上对中子电偶极矩敏感。中子是亚原子粒子，和质子一起，是原子核的基本组成部分。它们是电中性的，但原则上没有什么能阻止中子具有正负极，即所谓的“电偶极矩”（EDM）。宇宙起源的大爆炸理论预测，物质和反物质是等量产生的，它们早就应该湮灭了。目前可观测到的宇宙中物质比反物质多得多，因此应该存在导致宇宙演化中这种不平衡的过程。这些机制要求物质和反物质的行为与彼此的镜像略有不同。同样的潜在机制也预示着中子的EDM应该足够大，可以被观测到。因此，中子电火花加工实验试图阐明为什么宇宙中存在任何物质的问题。该合同支持仪器的建设，以提高对nEDM的灵敏度，超出当前限制的十倍，利用LANL升级的UCN源增加的超冷中子（UCN）产量。在发展nEDM搜索所需的知识和技术基础的过程中，学生和博士后研究人员将成为下一代科学家。自1951年以来，人们一直在进行中子电偶极矩（nEDM）的实验研究。到目前为止，还没有发现nEDM的证据。在许多理论场景中，成功的物质创造导致nEDM的严格下界在10^-27 e-cm的数量级。如果没有发现nEDM，这个实验，结合正在进行的原子和核系统中的EDM搜索，将在质量尺度上突破100 TeV以上违反物理的新对称性的极限。这超过了大型强子对撞机目前和未来的能量范围。另一方面，在这个水平上发现非零nEDM将揭示对称性违反的全新来源，有助于发展与宇宙学一致的自然基本力的统一理论。实现nEDM的目标灵敏度需要高密度的极化超冷中子（UCN）和能够控制系统效应的装置。实验设计基于Ramsey的分离振荡场方法，使用双室测量室，最先进的磁屏蔽，新型磁场配置和敏感磁强计（外部和共居）来控制系统。这种室温设计（不像许多正在开发的低温设计）将允许仪器在三年的时间内进行组装，测试和调试。该开发利用了印第安纳大学、肯塔基大学、LANL、密歇根大学和耶鲁大学现有的技术优势。该项目将与私营部门合作，为实验、原子磁力计建立一个磁屏蔽空间，并改进可能对医学成像技术产生影响的磁共振测量。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award supports the building of a new experiment at the Los Alamos National Laboratory (LANL) that will be sensitive to a neutron electric dipole moment at a very small scale. Neutrons are subatomic particles and, along with the proton, are the basic constituents of atomic nuclei. They are electrically neutral, but nothing in principle prevents the neutron from having positive and negative poles, a so-called "electric dipole moment"(EDM). Big-bang theories of the origin of the universe predict that matter and antimatter are created in equal parts, which should have annihilated long ago. The current observable universe has much more matter than antimatter, thus there should be processes which caused this imbalance in the evolution of the cosmos. These mechanisms require the behavior of matter and antimatter to be slightly different from each other's mirror image. The same underlying mechanism also predicts that the neutron should have an EDM large enough to be observable. Thus, neutron EDM experiments attempt to shed light on the question as to why there is any matter in the universe at all. This award supports the construction of instrumentation needed to improve the sensitivity to the nEDM by a factor of ten beyond current limits, taking advantage of the increased ultracold neutron (UCN) yield from the upgraded UCN source at LANL. In developing the knowledge and technical basis needed for the nEDM search, students and postdoctoral researchers will become the next generation of scientists.Experimental searches for the neutron electric dipole moment (nEDM) have been conducted since 1951. To date, no evidence for an nEDM has been found. In many theoretical scenarios, successful matter creation leads to strict lower bounds on the nEDM on the order of 10^-27 e-cm. If no nEDM is discovered, this experiment, in combination with ongoing EDM searches in atomic and nuclear systems, will push the limits on the mass scale for new symmetry violating physics above 100 TeV. This exceeds the current and future energy reach of the Large Hadron Collider. On the other hand, discovery of a nonzero nEDM at this level would reveal a completely new source of symmetry violations, contributing to the development of a unified theory of the fundamental forces of nature that is consistent with cosmology. Achieving the target nEDM sensitivity requires high densities of polarized ultra-cold neutrons (UCN) and an apparatus capable of controlling systematic effects. The experiment design is based on Ramsey's method of separated oscillatory fields using a two-cell measurement chamber, state-of-the-art magnetic shielding, novel magnetic field configurations, and sensitive magnetometry (both external and co-habitating) to control systematics. This room-temperature design (unlike many cryogenic designs under development) will allow the instrument to be assembled, tested, and commissioned on a three-year timescale. The development is leveraged by the existing technical strengths of Indiana University, the University of Kentucky, LANL, the University of Michigan, and Yale University. This project will partner with the private sector to build a magnetically shielded space for the experiment, atomic magnetometers, and improve magnetic resonance measurements which may have an impact on medical imaging technology.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.