Nucleon Structure and Nuclear Force Studies

有两个主要的研究领域，将探索与此研究补助金。 这两个领域都将为博士生提供培训和论文研究数据。 来自肯特州立大学的学生。 首先，该小组将研究核子的结构，即，中子和质子。 这里的主要项目是研究中子内部的电荷分布。 虽然中子没有净电荷，但组成中子的三个夸克都带电荷：上夸克带正电荷，两个下夸克带负电荷，三个夸克的电荷总和为零。 由于上夸克往往更靠近中子的中心，而下夸克更多地位于表面，因此中子内存在电荷分布，中心附近有更多的正电荷，表面附近有更多的负电荷。 这种电荷分布的精确测量将在托马斯杰斐逊实验室进行，使用肯特州立大学开发的设备。 这些测量具有相当重要的科学意义，因为它们为试图描述中子夸克结构的理论模型提供了约束。 第二个项目是研究质子的固有角动量（称为自旋）的起源。 这个项目已经在布鲁克海文国家实验室的相对论重离子对撞机（RHIC）的星星探测器系统上进行了几年;虽然质子的总自旋是已知的，但它的起源在组成质子的夸克的相互作用和运动方面还没有得到很好的理解。 第二个主要研究领域是研究原子核的“关联对”结构。 在原子核结构的主导模型中，中子和质子在原子核内的稳定量子轨道上相互独立地运动，就像原子核周围的电子轨道一样。 这个模型的开发者，被称为核壳模型，在1963年分享了诺贝尔奖。 布鲁克海文国家实验室和托马斯杰斐逊实验室最近的研究表明，大约20%的时间，一个给定的中子或质子，而不是在一个独立的轨道上运动，将是一对高速背靠背运动的粒子的一部分。 这些被称为“相关对”，因为它们的速度大小相似，但背靠背。 早期研究的一个有趣结果是，中子-质子对出现的频率是中子-中子对或质子-质子对的20倍。 这一发现对理解中子星具有重要意义。 这些结果来自对碳核的研究。 该小组将把这项工作扩展到氦核，并在比以前的工作更大的速度范围内观察相关对。 这项研究的更广泛的影响包括通过核物理学的参考期刊传播的对物理宇宙的更多理解，以及工业，医学物理学和学术界所需的博士级物理学家的培训。

There are two main research areas that will be explored with this research grant. Both of these areas will provide training and dissertation research data for Ph.D. students from Kent State. First, the group will be investigating the structure of the nucleon, i.e., of the neutron and proton. The primary project here is to study the distribution of electrical charge inside the neutron. Although the neutron has no net electrical charge, the three quarks that make up the neutron have electrical charge: plus charge for the "up" quark, and minus charge for the two "down" quarks, with the charges of all three summing up to zero. Since the up quark tends to be closer to the center of the neutron, and the down quarks more on the surface, there is a distribution of charge within the neutron, with more plus charge near the center, and more minus charge near the surface. Precision measurements of this charge distribution will be made at Thomas Jefferson Laboratory, using equipment developed at Kent State. These measurements are of considerable scientific importance, because they provide constraints on theoretical models attempting to describe the quark structure of the neutron. The second project is to study the origin of the intrinsic angular momentum, known as the spin, of the proton. This project has been underway for several years with the STAR detector system at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory; although the total spin of the proton is known, its origin in terms of the interactions and motions of the quarks that makeup the proton is not well understood. Measurements performed with the RHIC accelerator are now providing a clearer picture of the structure of the proton.The second main area of research is the study of the "correlated pair" structure of nuclei. In the dominant model of nuclear structure, the neutrons and protons move independently of each other in stable quantum orbits inside the nucleus, much like the orbits of the electrons surrounding the nucleus. The developers of this model, called the nuclear shell model, shared the Nobel Prize in 1963. Recent research at Brookhaven National Laboratory and Thomas Jefferson Laboratory has shown that about 20% of the time, a given neutron or proton, instead of moving in an independent orbit, will be part of a pair of particles moving back-to-back at high velocity. These are called "correlated pairs" because their velocities are similar in size, but back-to-back. A fascinating result from that earlier research is that neutron-proton pairs occur 20 times more often than neutron-neutron pairs or proton-proton pairs. This finding has important implications for understanding neutron stars. These results came from the study of the carbon nucleus. The group will be extending that work to the helium nucleus, and observing correlated pairs for a larger range of velocities than were explored in previous work. The broader impacts of this research include an increased understanding of the physical universe distributed through refereed journals of nuclear physics and the training of doctoral-level physicists needed in industry, medical physics, and academia.