Studies of Quark-Gluon Physics

这一NSF奖支持的研究计划将专注于研究质子和中子的内部结构，或者更一般地说，核子。这些基本粒子是我们周围所有可见物质的基石，构成了原子核。虽然众所周知，质子和中子是由非常轻的夸克组成的，在非常强的色力的作用下，这些夸克处于束缚状态，但关于这种束缚状态的详细结构，我们仍然知之甚少。特别是，我们对夸克动量在我们所处的三个空间维度中的分布知之甚少。我们目前的知识基本上局限于一个维度，类似于一个人的影子头像。该小组将在杰斐逊实验室领导两个实验，在这些实验中，高能电子束或光子束从氢和氚目标散射。在一项实验中，光子将与原子核内的夸克相互作用，并生成夸克相对于彼此的位置及其动量的地图。另一项实验将绘制出在广泛角度和能量范围内的散射图，从而产生核子的剪影图像。除了科学目标之外，拟议的实验设置、数据获取和分析活动将继续为本科生、研究生和博士后研究助理提供教育和研究经验。在以一流加速器设施为基础的国际合作环境中工作，将拓宽小组成员的视野和兴趣，并有助于培训该国未来的STEM劳动力。这项为期三年的研究计划将通过检查夸克被托马斯·杰斐逊国家加速器设施的高强度加速器产生的高能a光子从核子抛出时产生的亚原子粒子的动量，来研究夸克的3D动量分布。核物理界将首次使用具有明显偏振的光子来研究这种夸克弹射过程，从而能够研究与1/2夸克自旋相关的效应。半包含深度非弹性散射(SIDIS)的单自旋不对称性测量将被用来研究核子的横向动量相关部分子分布(TMD)和碎裂函数。SIDIS测量正在成为杰斐逊实验室12 GeV CEBAF的旗舰项目，也是新宣布的将于未来十年在布鲁克黑文国家实验室建造的电子-离子对撞机。研究活动将以JLab实验为中心，使用SIDIS测量带电介子和介子与氢和重氢目标的截面。这项工作的部分动机是测试用于SIDIS过程的因式分解框架，其中从此类测量中提取TMD是基于该因式分解框架的。另一项实验集中于对SIDIS带电的质子从氢靶和氢靶中产生的质子进行L-T分离，以检验来自SIDIS的R是否与来自包含DIS的R相同，其中R是纵向到横向的截面。预计的测量结果将显著改善现有的来自先前实验的稀缺数据，并促进我们对潜在生产机制的了解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The research program supported by this NSF award will focus on the study of the inner structure of the proton and neutron, or more generically, the nucleon. These basic particles are the building blocks for all the visible matter around us, making up the atomic nucleus. While it is well known that the proton and neutron are composed of very light quarks held in a bound state by the very strong color force, there is still little information available about the detailed structure of this bound state. In particular, we know very little of the distribution of the quark momentum in the three space dimensions we live in. Our present knowledge is essentially limited to one dimension, similar to a shadow profile picture of a person. This group will lead two experiments at Jefferson Laboratory in which beams of high energy electrons or photons are scattered from hydrogen and deuterium targets. In one experiment photons will interact with the quarks inside the nucleus and produce a map of where the quarks are relative to each other and their momentum. The other experiment will map out the scattering over a wide range of angles and energies that produce silhouette-like images of the nucleon. Beyond the scientific goals, the proposed experiment setup, data acquisition and analysis activities will continue to offer education and research experience to undergraduates, graduate students, and postdoctoral research associates. Working in the environment of an international collaboration based at a premier accelerator facility will broaden the perspective and interests of the group members and help to train the future STEM workforce of the country.This three-year research program will study the 3D momentum distribution of the quarks by examining the momentum of the sub-atomic particles they produce when ejected from the nucleon by a high-energy a photon, produced by the high intensity accelerator at the Thomas Jefferson National Accelerator Facility. For the first time, the nuclear physics community will study this quark ejection process using photons with distinct polarization, allowing for the study of effects related to the quark spin of ½. Single spin asymmetry measurements from semi-inclusive deep-inelastic-scattering (SIDIS) will be used to study the transverse momentum dependent parton distribution (TMD) and fragmentation functions of the nucleon. SIDIS measurements are becoming a flagship program both at the 12-GeV CEBAF at Jefferson Lab, and also the newly announced electron-ion-collider to be built at Brook Haven National Lab in the coming decade. The research activities will center around JLab experiments using SIDIS to measure the cross section of charged pions and kaons from hydrogen and deuterium targets. This work is partially motivated as a test of the factorization framework used for SIDIS processes where the TMD extraction from such measurements is based upon. Another experiment focuses on performing L-T separations of SIDIS charged pion production from hydrogen and deuterium targets to test whether R from SIDIS is the same as R from inclusive DIS, where R is the longitudinal to transverse cross section. The projected measurements will significantly improve the existing scarce data from prior experiments and advance our knowledge about the underlying production mechanism.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.