NSF-BSF: Exploring the Proton Radius Puzzle and Phenomena Beyond the Standard Model with Low-energy Lepton Scattering

该奖项为迈克尔·科尔博士和他在汉普顿大学的团队提供资金，汉普顿大学是美国弗吉尼亚州历史上的黑人学院和大学。该小组在瑞士保罗-谢勒研究所正在准备的缪子散射实验(MUSE)和美国托马斯·杰斐逊国家加速器设施(杰斐逊实验室)的暗光项目中发挥着核心作用。缪斯计划致力于研究所谓的质子半径之谜，这是核物理学中一个非常突出的话题。该实验将通过轻子-质子弹性散射高精度测量质子电荷半径，并将在基态水平上比较任一电荷的µ子和电子与质子的相互作用。这项实验将严重限制对这个谜题的可能解释，并有可能揭示标准模型以外的新物理。杰斐逊实验室正在筹备的暗光实验旨在发现一种与第五种相互作用相关的新粒子，该粒子适合解释粒子物理中观察到的几个异常现象，同时提供与暗物质的联系。这两个项目都为处于国际核物理和粒子物理研究前沿的学生和博士后提供了备受瞩目的机会。PI的研究项目具有多个方面，为国内外尖端教育和研究目的提供了极好的机会。这项提议将汉普顿大学最先进的探测器开发与其在PSI和杰斐逊实验室的前沿研究中的应用结合起来。这为少数族裔学生(主要是非洲裔美国人)和博士后研究人员在一流研究设施中提供了新的研究和教育机会。宝石探测器在缪斯和暗光环境中的开发和运行将有利于推动这项仍具有潜在应用前景的新技术在其他实验中以及在医疗领域的应用。缪斯实验已经被提出并被批准，以提供关键的洞察力，以寻求解释所谓的质子半径之谜-分别用电子探测器和缪子探测器测量质子电荷半径之间超过五个标准偏差的差异。可能的解释还包括超越标准模型的新物理。缪斯实验旨在解决迄今为止核科学和粒子科学中最紧迫的问题之一。MUSE使用混合的Muon和电子束(Mu+，e+，Mu-，e-)来精确测量轻子-质子弹性散射截面和质子形状因子，目的是提取每个探测器的质子电荷半径。它将以最高的精度，独立和决定性地建立模型，确定在电子与缪子散射中是否观察到任何质子电荷半径差异。同时，它将确定双光子交换的作用，并为理论提供严格的约束。科尔博士是缪斯项目的共同发起人之一。科尔博士的团队在缪斯的作用对这个项目至关重要。这个项目的重点是在MUSE上用GEM探测器以一种以前在低束能下从未做过的方式进行高分辨率束流粒子跟踪的挑战性任务。该跟踪器暴露在高速率密度和束流密度下，并且需要以几千赫的触发速率有效地运行。杰斐逊实验室的暗光第一阶段项目包括在17 MeV/c2附近的质量区域集中搜索暗光子或中性玻色子，在那里已经报告了第五种力量载体的证据。这一奖励反映了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。

This award provides funding for Dr. Michael Kohl and his group at Hampton University, a Historically Black College und University in Virginia, USA. The group has a core function in the Muon Scattering Experiment (MUSE) in preparation at Paul-Scherrer Institute in Switzerland, and in the DarkLight project at the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory) in the US. The MUSE project is a dedicated investigation of the so-called proton radius puzzle, a very prominent topic in nuclear physics. The experiment will measure the proton charge radius with high precision via lepton-proton elastic scattering, and will compare the interactions of muons and electrons of either charge with the proton at a fundamental level. The experiment will severely constrain possible explanations of the puzzle and has the potential to reveal new physics beyond the Standard Model. The DarkLight experiment in preparation at Jefferson Lab aims to discover a new particle associated with a fifth interaction suited to explain several observed anomalies in particle physics while offering a connection to dark matter. Both projects offer high-profile opportunities for students and postdocs at the forefront of international nuclear and particle physics research. The PI's research program has many facets and offers excellent opportunities for cutting-edge education and research purpose domestically and abroad. This proposal combines state-of-the-art detector development at Hampton University with its application in forefront research at PSI and at Jefferson Lab. This provides new research and educational opportunities at first-class research facilities for students from minority populations, predominantly African-Americans, and postdoctoral researchers. The development and operation of GEM detectors in the MUSE and DarkLight environments will be beneficial to advance this still novel technology with potential future applications in other experiments, as well as in the medical sector. The MUSE experiment has been proposed and approved to provide key insight in the quest to explain the so-called proton radius puzzle - the over five-standard deviation discrepancy between proton charge radius measurements with electronic and muonic probes, respectively. Possible explanations also include new physics beyond the Standard Model. The MUSE experiment aims to address one of the most pressing questions in nuclear and particle science to date. MUSE uses mixed muon and electron beams of either charge (mu+, e+, mu-, e-) to make precise measurements of the lepton-proton elastic scattering cross sections and proton form factors, with the goal to extract the proton charge radius for each probe. It will determine with the highest precision, model independently and conclusively, if there is any proton charge radius difference observed in electron versus muon scattering. At the same time it will determine the role of two-photon exchange and provide tight constraints on theory. Dr. Kohl is one of the co-initiators of the MUSE project. The role of Dr. Kohl's group in MUSE is essential to this project. This project focuses on the challenging task of high-resolution beam particle tracking at MUSE with GEM detectors, in a way not done before at low beam energies. The tracker is exposed to high rate density and beam flux, and needs to operate efficiently at a trigger rate of a few kHz. The DarkLight Phase-I project at Jefferson Lab includes a focused search for a dark photon or neutral boson in the mass region around 17 MeV/c2, where evidence for a fifth-force carrier has been reported.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.