Studies of Quark-Gluon Physics

NSF资助的研究项目将重点研究质子和中子的内部结构，或者更一般地说，核子的内部结构。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。众所周知，质子和中子是由非常轻的夸克组成的，它们在非常强的色力作用下处于束缚状态，但关于这种束缚状态的详细结构的信息仍然很少。特别是，我们对夸克动量在我们生活的三维空间中的分布知之甚少。我们目前的知识基本上局限于一个维度，类似于一个人的阴影侧面照片。这个小组将在杰斐逊实验室领导两个实验，其中高能电子或光子束从氢和氘的目标散射。在一项实验中，光子将与原子核内的夸克相互作用，并绘制出夸克彼此相对位置及其动量的地图。另一个实验将绘制出在大范围角度和能量范围内的散射，从而产生类似核子轮廓的图像。在科学目标之外，拟议的实验设置，数据采集和分析活动将继续为本科生，研究生和博士后研究人员提供教育和研究经验。在一个基于一流加速器设施的国际合作环境中工作，将拓宽小组成员的视野和兴趣，并有助于培养该国未来的STEM劳动力。这个为期三年的研究项目将通过检查亚原子粒子的动量来研究夸克的三维动量分布，这些粒子是由高能光子从核子中射出的，由托马斯·杰斐逊国家加速器设施的高强度加速器产生的。核物理学界将首次使用具有不同极化的光子来研究这种夸克喷射过程，从而可以研究与夸克自旋1 / 2相关的效应。半包容深度非弹性散射（SIDIS）的单自旋不对称测量将用于研究核子的横向动量依赖的部分子分布（TMD）和碎片函数。SIDIS的测量正在成为杰弗逊实验室12 gev CEBAF的旗舰项目，也将成为未来十年在布鲁克海文国家实验室新宣布的电子-离子对撞机的旗舰项目。研究活动将围绕JLab的实验展开，利用SIDIS来测量来自氢和氘目标的带电介子和介子的横截面。这项工作的部分动机是作为用于SIDIS过程的分解框架的测试，其中从这些测量中提取TMD是基于的。另一个实验重点是对氢和氘靶的SIDIS带电介子产生进行L-T分离，以测试SIDIS的R是否与包容DIS的R相同，其中R为纵横截面。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，并提高我们对潜在生产机制的认识。该奖项反映了美国国家科学基金会的法定使命，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。

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.