Probing Nucleon Structure Through Muon and Photon Scattering

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尺寸测量结果不一致，但比它们精确得多。该奖项支持的研究旨在通过在μ子质子散射实验（MUSE）中同时测量质子上的μ子和电子散射来解决这个被称为“质子半径之谜”的问题。除了确定质子的大小，该小组还将花费少量时间通过测量被称为极化率的量来研究质子和中子的内部结构和动力学。这些测量将通过质子和中子的散射光进行。实验将在瑞士、德国和美国的实验室进行。 通过这些实验，除了获得有关质子和中子的知识外，博士后研究人员，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。质子和中子的极化率也将通过它们对康普顿散射中测量的束和目标极化不对称性的影响进行研究。在德国美因茨的Mainzer Microtron的A2合作中对液氢和氦3和4进行精确的横截面测量，并在三角大学核实验室的高强度伽马源（HIGS）中进行较低能量的测量。 该项目涉及参与和领导的建设，数据采集和分析的MUSE通过PI，研究生和博士后的支持。它将导致精确的，同时弹性μ子和电子散射数据，以及质子和中子的标量极化率的精确测量。

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 resulted in a proton size measurement much smaller than expected. This measurement disagreed with, but was much more precise than, all the other proton size measurements to date. The research supported by this award aims to resolve this issue, known as the "Proton Radius Puzzle" by making a simultaneous measurement of muon and electron scattering on the proton in the Muon Proton Scattering Experiment (MUSE). In addition to determining the proton size, the group will spend a small amount of its time investigating the internal structures and dynamics of the proton and neutron, by measuring quantities known as the polarizabilities. These measurements will be made by scattering light from protons and neutrons. Experiments will take place at laboratories in Switzerland, Germany and the US. Through these experiments, in addition to gaining knowledge about protons and neutrons, the postdoctoral researchers, 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. The polarizabilities of the proton and neutron will be also investigated via their influence on beam and target polarization asymmetries measured in Compton Scattering. Precise cross section measurements on liquid hydrogen and helium three and four within the A2 collaboration at the Mainzer Microtron in Mainz, Germany, and at lower energies in the High-Intensity Gamma Source (HIGS) at the Triangle Universities Nuclear Laboratory. This project involves participation in and leadership of construction, data taking and analysis of MUSE through the support of the PI, a graduate student, and postdoc. It will result in precise, simultaneous elastic muon and electron scattering data, and precise measurements of the scalar polarizabilities of the proton and neutron.