LEAPS-MPS: Precision Measurements of Neutron Beta Decay to Test Fundamental Symmetries

该奖项支持东肯塔基大学的Fry博士的一个项目，该项目将通过旨在精确确定中子寿命及其两个衰变参数（称为“a”和“b”）的研究活动影响科学和社会，以及培训和指导技术领域的本科生，为他们在STEM领域的职业生涯做好准备。精确地确定中子的衰变参数可以为标准模型提供灵敏的测试，实现这一目标已被核科学咨询委员会确定为当前核科学长期计划的高度优先事项。令人兴奋的初步结果已经引起了公众的兴趣，并将随着这项工作的进一步成果继续引起公众的兴趣。中子“a”和“b”（Nab）实验和光束寿命3 （BL3）的尺度及其对物理许多子领域的技术的使用，使学生能够亲自参与，并发展对物理原理和实验技术的广泛理解。该项目将帮助EKU培养积极进取的学生，为更大规模的合作提供研究机会，并开展基于团队的科学研究。该奖项将以生活工资雇佣EKU的学生，这将有助于留住学生，并通过让他们参与专业活动来提高学生未来的成功，从而进一步增加科学劳动力。物理学标准模型的基石之一是夸克混合矩阵（CKM矩阵）的统一性。这种对称性可以通过结合精确测量轴矢量和矢量耦合常数的比值以及中子寿命来检验。目前，使用不同的方法测量中子寿命是相互冲突的，解决这种差异是一个高度的智力优先事项。此外，中子寿命具有宇宙学意义，因为它是大爆炸核合成（BBN）过程中轻元素形成的关键因素。中子寿命的不确定性对原始氦丰度YP的不确定性贡献最大。在这些宇宙学模型中，YP与宇宙膨胀和有效中微子种类的数量等重要参数有关；解决中子寿命之谜是核科学的头等大事，在宇宙学和粒子物理学的相互作用中具有重要意义。该奖项将涉及学生在东肯塔基大学和橡树岭国家实验室的动手经验。以学生为中心的项目将包括解决Nab实验中重要的系统效应，通过进行原位定时研究来表征硅探测器小于或等于1ns，为Nab和BL3实验的系统研究开发复杂的蒙特卡罗模拟，并为BL3实验开发数据分析服务器。这项工作将使学生在地方大学获得非凡的经历，前往国家实验室，体验更大的合作，并帮助他们在科学队伍中发挥有意义的作用。该项目由数学和物理科学理事会物理系和促进竞争性研究的既定计划（EPSCoR）共同资助。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 Dr. Fry at Eastern Kentucky University in a project that will impact science and society through research activities aimed at precisely determining the neutron lifetime and two of its decay parameters (known as “a” and “b”), as well as training and mentoring undergraduate students in technical areas that will prepare them for careers in STEM fields. Precisely determining the neutron’s decay parameters can provide sensitive tests of the Standard Model and achieving that has been identified as a high priority in the current Long-Range Plan for Nuclear Science by the Nuclear Science Advisory Committee. Exciting preliminary results have already generated public interest and will continue to do so with further results from this work. The scales of the neutron “a” and “b” (Nab) experiment and the Beam Lifetime 3 (BL3) and its use of techniques from many subfields of physics lends itself to hands-on student participation and the development of a broad understanding of physical principles and experimental techniques. The project will help train motivated students at EKU, provide research opportunities in larger scale collaborations, and conduct team-based science. The award will employ students at a living wage at EKU, which will help retain students and increase future student success by keeping them engaged in activities in their major, therefore further adding to the scientific workforce.One of the cornerstones of the Standard Model of physics is the unitarity of the quark mixingmatrix (CKM matrix). This symmetry can be tested by combining precise measurements of the ratio of the axial-vector and vector coupling constants, and the neutron lifetime. Currently, measurements of the neutron lifetime using different methods are in conflict with each other and resolving this discrepancy is of high intellectual priority. Additionally, the neutron lifetime has cosmological implications as it was a key factor in the formation of the light elements during Big Bang Nucleosynthesis (BBN). The uncertainty in the neutron lifetime is the largest contribution to the uncertainty in the primordial helium abundance, YP. In these cosmological models, YP is related to important parameters such as the expansion of the universe and the number of effective neutrino species; resolving the neutron lifetime puzzle is top priority in nuclear science with implications in the interplay of cosmology and particle physics. The award will involve students in hands-on experiences in the lab at Eastern Kentucky University and at Oak Ridge National Lab. Student-centered projects will include addressing an important systematic effect in the Nab experiment by conducting an in-situ timing study to characterize silicon detectors to less than or equal to 1 ns, developing complex Monte Carlo simulations for systematic studies in the Nab and BL3 experiments, and to develop a data analysis server for the BL3 experiment. This work will give students an extraordinary experience at a regional university, travel to a national lab and experience with a larger collaboration and help them carve out meaningful roles in the scientific workforce. This project is jointly funded by the Division of Physics within the Mathematical and Physical Sciences Directorate and the Established Program to Stimulate Competitive Research (EPSCoR).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.