Multi-Probe Investigation of the Nucleon

质子、中子和电子是我们最熟悉的所有物质的组成部分。尽管科学努力了解它们的本质，但关于它们还有许多事情有待了解。2010年，对质子大小的测量得出的结果比预期的要小得多。这一测量结果与迄今为止所有其他质子大小的测量结果不一致，但要精确得多。从那时起，许多人试图用不同的方法重新测量质子的大小，但差异仍然存在。该奖项支持的研究旨在通过在μ子质子散射实验（MUSE）中首次同时测量质子上的μ子和电子散射来解决这个被称为“质子半径之谜”的问题。通过这个实验，博士后、本科生和研究生除了获得关于质子的知识外，还将获得现代检测技术、模拟和重建软件的知识和经验，这些技术和软件在工业或医学成像等许多应用中都有应用。他们还将与来自世界许多国家的研究人员进行文化交流，培养他们的沟通、组织和领导能力。MUSE将通过弹性μ子散射进行世界上第一次质子半径的测量，其精度可以解决4%质子半径的难题。该实验将在瑞士的保罗·谢勒研究所进行。在MUSE实验中同时测量质子上的弹性e + / e-和mu + /mu-负散射，将解决质子半径难题：在介子氢的激发光谱中测量到的质子的电荷半径与在原子氢的激发光谱中测量到的质子的电荷半径之间的7西格玛差异。同时使用电子和μ子进行测量，提高了系统的不确定度，并提供了对轻子普适性的检验。测量两种电荷状态可以直接测量和确定，然后抵消介子和电子散射中的任何双光子效应。本项目由项目负责人、一名研究生、一名本科生和一名博士后共同参与并领导MUSE的数据采集和分析工作。它将产生精确的，同时的弹性μ子和电子散射数据。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。

Protons, neutrons, and electrons are the building blocks of all matter with which we are most familiar. Despite the scientific efforts to comprehend their nature, there are many things about them that remain to be understood. In 2010, a measurement of the size of the proton gave a much smaller than expected result. This measurement disagreed with, but was much more precise than, all the other proton size measurements to date. Since that time, many other people have tried to re-measure the proton size using different approaches, but the discrepancy persists. The research supported by this award aims to resolve this issue, known as the "Proton Radius Puzzle" by making the first simultaneous measurement of muon and electron scattering on the proton in the Muon Proton Scattering Experiment (MUSE). Through this experiment, in addition to gaining knowledge about protons, the postdoctoral researcher, undergraduate, and graduate students will gain knowledge and experience of modern detection techniques, and simulation and reconstruction software, which are employed in many applications such as industrial or medical imaging. They will also participate in cultural exchanges with researchers from many countries worldwide, and develop their communication, organization, and leadership skills.MUSE will make the world's first measurement of the proton radius via elastic muon scattering at a precision which can address the 4% proton radius puzzle. The experiment will be performed at the Paul Scherer Institute in Switzerland. The simultaneous measurement of elastic e-plus / e-minus and mu-plus/mu-minus scattering on the proton in the MUSE experiment will allow resolution of the proton radius puzzle: the 7-sigma discrepancy between the charge radius of the proton measured in the excitation spectrum of muonic hydrogen and that measured in the excitation spectrum of the atomic hydrogen. Measuring with both electrons and muons simultaneously improves the systematic uncertainty, and provides a test of lepton universality. Measuring both charge states allows for the direct measurement and determination, and then cancellation, of any two-photon effects in both muon- and electron-scattering. This project involves participation in and leadership of data taking and analysis of MUSE through the support of the PI, a graduate student, undergraduate student, and a postdoc. It will result in precise, simultaneous elastic muon and electron scattering data.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.