Collaborative Research: Equipment for the PSI MUSE Experiment

众所周知，质子和中子是由夸克和胶子组成的。夸克和胶子产生了有限大小的质子，它比单个原子的大小小10，000倍。这个项目的目标是测量质子的大小。 一个正在进行的谜题是，当用原子氢测量时，质子的大小似乎与其对应物（称为μ子氢）不同，其中氢原子中的电子被其更重的表亲μ子取代。该项目将专门建造用于实验的设备，以提供质子半径的独立测量。除了该项目的直接科学目标外，这些实验还为学生和年轻科学家提供了在现代科学实验的国际合作中工作的经验和培训，以及最先进的技术。用μ介子氢测量的质子半径与用电子-质子散射测量的质子半径之间的七个标准偏差可能表明物理学超越了粒子物理学的标准模型，或者由传统物理学的新颖方面或者由从实验数据中提取半径的问题引起。μ子散射实验（MUSE）旨在解决质子半径之谜。MUSE在瑞士的Paul Scherrer研究所（PSI）使用混合的π介子，μ介子和电子束。MUSE将通过μ子-质子散射和电子-质子散射来确定质子半径，除了用正负轻子进行这些反应之外。这不仅降低了系统的不确定性，而且还提供了对双光子交换贡献的灵敏度，这可能是早期实验中出现的一些差异的原因。该合作项目将在2016年9月至2018年8月期间支持MUSE的建设。PSI还将进行持续的测试和调试活动，包括2017年底使用部分光谱仪进行彩排。蒙哥马利学院负责测试计算机数据采集和相关电子设备。

It is well known that protons and neutrons are made from constituents, called quarks and gluons. The quarks and gluons give rise to a finite size of the proton, which is about 10,000 times smaller than the size of a single atom. The goal of this project is to measure the size of the proton. An on-going puzzle is that the proton size appears to be different when measured with atomic hydrogen as compared with its counterpart, called muonic-hydrogen, where the electron in a hydrogen atom is replaced by its heavier cousin, the muon. This project will specifically build equipment to be used in an experiment to provide an independent measurement of the proton radius. In addition to the direct scientific goals of the project, the experiments provide students and young scientists experience and training in working in the international collaborations of modern scientific experiments, with state of the art technology.The seven standard deviation discrepancy between the proton radius measured with muonic hydrogen and with electron-proton scattering may point to physics beyond the standard model of particle physics, or result from novel aspects of conventional physics or from issues in extracting the radius from experimental data. The Muon Scattering Experiment (MUSE) aims to resolve the proton radius puzzle. MUSE uses a mixed pion, muon and electron beam at the Paul Scherrer Institute (PSI) in Switzerland. MUSE will determine the proton radius through both muon-proton scattering and electron-proton scattering, in addition to performing these reactions with positive and negative leptons. This not only reduces systematic uncertainties but also provides sensitivity to two-photon exchange contributions that may be responsible for some of the discrepancies seen in earlier experiments. This collaborative project supports the construction of MUSE over the period September 2016 - August 2018. There will also be ongoing testing and commissioning activities at PSI, including a dress rehearsal run with a partial spectrometer in late 2017. Montgomery College is responsible for testing the computer data acquisition and associated electronics.