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基本组成部分。尽管科学家们努力去理解它们的本质，但关于它们还有许多事情有待理解。2010年，对质子大小的测量给出了比预期小得多的结果。这一测量结果与迄今为止所有其他质子尺寸测量结果不一致，但比它们精确得多。从那时起，许多其他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，除了获得有关质子的知识外，博士后研究员，本科生和研究生还将获得现代检测技术以及模拟和重建软件的知识和经验，这些技术和软件可用于工业或医学成像等许多应用。他们还将与来自世界各地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将在世界上首次通过弹性μ子散射测量质子半径，其精度可以解决质子半径4%的难题。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-散射和μ +/μ-散射将解决质子半径难题：μ氢激发光谱中测量的质子电荷半径与原子氢激发光谱中测量的质子电荷半径之间的7 σ差异。同时用电子和μ子测量提高了系统的不确定性，并提供了轻子普适性的测试。测量两种电荷状态允许直接测量和确定，然后消除μ子和电子散射中的任何双光子效应。 该项目涉及参与和领导的数据采集和分析的MUSE通过PI的支持，研究生，本科生，和博士后。该奖项反映了NSF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.