RUI: Fundamental Symmetry Experiments with Muons

RUI：μ子的基本对称性实验

• 批准号: 1505887
• 负责人: Frederick Gray
• 金额: $ 13.5万
• 依托单位: Regis University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505887&HistoricalAwards=false
• 关键词: RUI; Fundamental; Symmetry; Experiments; Muons

The study of fundamental symmetries in the field of nuclear physics explores the nature of the matter, energy, and forces that define the universe and that have allowed stars, planets, and life to emerge and flourish. This award will support the PI and undergraduate students to work on two experiments that will further our understanding of that universe. The first experiment, called MuSun, addresses one of the most important limitations of calculations related to the proton-proton fusion process that releases most of the energy in stars like the Sun. It will provide data that will calibrate the least precise parts of these calculations and can also be applied to other important nuclear reactions. The second, known as the Muon g-2 experiment, tests our Standard Model of particles and their interactions. While this model has been remarkably successful, it is not complete. The previous generation of this experiment uncovered a strong hint of a discrepancy between its measurement and the Standard Model's prediction; the new experiment will probe it with enough precision to potentially claim a discovery.Students will have opportunities to carry out guided research related to the larger physics goals, to work at major research facilities, and to attend conferences and collaboration meetings. This grant will provide opportunities to involve and support a talented and diverse group of science students that includes women, members of underrepresented ethnic groups, and first-generation college students.MuSun measures the rate of muon capture in deuterium, a fundamental two-nucleon process that provides a calibration of effective field theories of weak interactions in light nuclei. The muon capture process studied by the MuSun experiment is analogous to reactions that include proton-proton fusion and the deuteron breakup reactions that were used to detect neutrinos at the Sudbury Neutrino Observatory. The MuSun result will dramatically improve the precision of the low-energy constants describing two-nucleon terms in chiral effective field theories that describe these reactions. The Muon g-2 experiment at Fermilab will be the group's primary focus for this grant period. This experiment measures the anomalous magnetic moment of the muon by observing the rate of spin precession of a muon beam as it circulates in a precisely shimmed storage ring magnet. The spin polarization precesses because of coupling to virtual particles, including all of the particles described by the Standard Model and potentially any new, as-yet-undiscovered particles and interactions that are beyond it. The Regis group will be responsible for the implementation, installation, commissioning, and analysis for the fiber harp beam monitors and entrance counters for this experiment. The measurement clearly has the potential to discover new physics beyond the Standard Model. When the existing precision of 0.5 parts per million from the Brookhaven National Laboratory experiment is compared with modern Standard Model calculations, there is a discrepancy of more than three standard deviations; the probability of a fluctuation at this level by chance is less than one in a thousand. As the precision of the experiment reaches its 0.14 part-per-million goal, the discrepancy could exceed the discovery threshold of five standard deviations. Such a finding could represent the discovery of supersymmetry, new gauge bosons such as dark photons, or other new particles or interactions.

对核物理领域基本对称性的研究探索物质、能量和力的性质，这些物质、能量和力定义了宇宙，并使恒星、行星和生命得以出现和繁荣。这个奖项将支持PI和本科生在两个实验上工作，这两个实验将促进我们对宇宙的理解。第一个实验名为MuSun，解决了与质子-质子聚变过程有关的计算的最重要限制之一，该过程释放了太阳等恒星中的大部分能量。它将提供数据，以校准这些计算中最不精确的部分，也可以应用于其他重要的核反应。第二个实验被称为Muon g-2实验，它测试我们的粒子及其相互作用的标准模型。尽管这种模式非常成功，但它并不完整。上一代实验发现了其测量结果与标准模型预测之间存在差异的强烈迹象；新实验将以足够高的精度对其进行探测，有可能宣布一项发现。学生将有机会开展与更大的物理目标相关的指导研究，在主要研究机构工作，并参加会议和合作会议。这笔赠款将提供机会，让有才华的、多样化的理科学生群体参与进来，并为他们提供支持，其中包括女性、未被充分代表的民族成员和第一代大学生。MuSun测量了重离子在重气中的俘获率，这是一个基本的两核子过程，提供了对轻核中弱相互作用的有效场论的校准。MuSun实验研究的Muon俘获过程类似于萨德伯里中微子天文台用来探测中微子的质子-质子聚变和氚裂解反应。MuSun的结果将极大地提高手征有效场理论中描述两核子项的低能常数的精度，这些项描述了这些反应。费米实验室的Muon g-2实验将是该小组在这一赠款期间的主要重点。这项实验通过观察介子束在精确匀场的存储环磁体中循环时的自旋进动速度来测量介子的反常磁矩。自旋极化是由于耦合到虚拟粒子而进行的，包括标准模型描述的所有粒子，以及潜在的任何新的、尚未发现的粒子和超出标准模型的相互作用。瑞吉斯集团将负责实施、安装、调试和分析本实验中的光纤竖琴波束监测器和入口计数器。这种测量显然有可能发现超越标准模型的新物理。布鲁克海文国家实验室实验的现有精度为百万分之零点五，与现代标准模型计算相比，误差超过三个标准差；偶然在这个水平上波动的概率不到千分之一。随着实验的精确度达到百万分之0.14的目标，偏差可能会超过发现五个标准偏差的门槛。这样的发现可能代表着超对称性的发现，暗光子等新规范玻色子的发现，或其他新粒子或相互作用的发现。