Study of Specific Properties of Hadrons via Precision Experiments at Jefferson Lab

该研究项目集中在弗吉尼亚州托马斯·杰斐逊国家加速器设施的两个高度评价的实验项目上。其中一个实验将测量质子半径，这是物理学中最基本的量之一。它与质子的结构直接相关，而质子是可见物质的基本组成部分。本研究将继续开发和构建新型氢靶，进行新的电子-质子散射实验，直接给出更高精度的质子半径。第二个项目将以高精度测量一种名为eta介子的粒子的寿命，并将其与量子色动力学基础理论（QCD）的理论预测进行比较。该项目还将为本科生和研究生提供独特的机会，让他们积极参与许多不同领域的跨学科研究：新硬件和前沿软件开发；大规模数据分析和现代计算问题。通过这种方式，研究工作有助于发展急需的高科技劳动力。质子电荷半径作为物理学中最基本的物理量之一，将在原子物理和核物理中产生深远的影响。这个量目前发展的实验情况限制了里德伯常数的确定，里德伯常数是迄今为止自然界中最基本和最精确的常数之一。实验结果可能对标准模型之外的新物理学很敏感。预计的介子寿命测量精度为3%，将有可能解决primakoff型和正电子对撞机实验之间长期存在的差异。它还将以一种直接的、与模型无关的方式提高轻夸克质量比。

This research project is focused on two highly rated experimental projects at the Thomas Jefferson National Accelerator Facility in Virginia. One experiment will measure the proton radius, one of the most fundamental quantities in physics. It is directly related to the structure of the proton, which is a basic constituent block of visible matter. This research will continue the development and construction of a novel hydrogen target to perform a new electron-proton scattering experiment, directly giving the proton radius with higher precision. The second project will measure the lifetime of a particle called the eta meson with high precision, which will be compared with theoretical predictions from the fundamental theory of Quantum Chromodynamics (QCD). This project will also provide unique opportunities for students, both undergraduate and graduate, to be actively engaged in many different areas of interdisciplinary research: new hardware and cutting-edge software development; large scale data analysis and modern computational problems. In this way the research effort contributes to the development of a much-needed high tech workforce. As one of the most fundamental quantities in physics, the proton charge radius new independent measurement will have far reaching effect in both atomic and nuclear physics. The currently developed experimental situation with this quantity limits the determination of the Rydberg constant, one of the basic and the most precisely known constant in nature up to now. The experimental results may be sensitive to new physics beyond the Standard Model. The projected 3% accuracy of the eta-meson lifetime measurement will potentially resolve the long-standing discrepancy between the Primakoff-type and electron-positron collider experiments. It will also improve the light quark mass ratio in a direct and model independent way.