RUI: Probing the Structure of Nucleons in Omega Meson Electroproduction

准确地了解原子核内部如何产生这种强大的力，是当今核物理学家面临的最大智力挑战之一。这种强大的力产生了核力，使质子和中子在原子核内结合在一起。这种强大的力是通过胶子粒子的交换来调节的。正是这种胶子相互作用占据了核子的大部分质量。核子是质子或中子的总称。核子是由嵌入在起泡的胶子海洋中的三个价夸克形成的。然而，我们对质子和中子是如何从它们的夸克和胶子成分中构造出来的知识充其量也是最基本的。入射到核子上的高能粒子，如电子，可以直接与内部的价夸克之一相互作用，导致夸克经历自旋翻转或赋予夸克轨道或径向激发。随着夸克处于更高的能态，激发的核子变得更大。这些激发态被称为核子共振(N*S)，存在的时间很短--大约是万亿分之一秒(10−24 S)，然后会衰变成其他粒子。产生的粒子的类型以及它们在空间中的分布方式提供了关于质子组成的关键信息。拉马尔大学主要是一所本科院校。在过去的二十年里，PI已经建立了让本科生参与他的研究项目的良好记录，这种做法将在这个奖项的支持下继续下去。杰斐逊实验室(弗吉尼亚州纽波特新闻)和ELSA(德国波恩)在理解核子共振方面的这些基本测量，以及该奖项的强烈教育重点，与核科学咨询委员会2015年长期计划的主要目标一致，从而服务于国家利益。该研究计划是利用杰斐逊实验室和ELSA的一束线偏振光子和/或极化电子来研究核子的基本性质和结构。从夸克与胶子的结合、夸克到无色强子的结合、核子到原子核的结合，以及大原子核的集体行为，从夸克到胶子的结合，到大核子的集体行为，强的核相互作用是造成这一现象的原因。这个研究小组寻求以下问题的答案：当海夸克和胶子的贡献最小时，价夸克如何自组装；胶子如何与夸克结合以增加当前夸克的质量到组成夸克的质量；夸克如何在核子内部共振，形成受激发的夸克集合。PI和他的本科生团队的目标是从夸克和胶子的集合中了解浮现的行为和结构。这些研究的探测器将是欧米伽介子。通过欧米伽介子清晰而明确的信号探测N*S的结构有很大的发现潜力。此外，作为动量传递的函数，通过欧米伽模式衰减的重子共振的数据非常缺乏。这一奖项反映了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。

Understanding exactly how the strong force is generated inside the nucleus is one of the greatest intellectual challenges facing nuclear physicists today. The strong force gives rise to the nuclear forces that bind protons and neutrons together inside the nucleus. The strong force is mediated by the exchange of particles known as gluons. It is this gluon interaction that accounts for most of mass of the nucleon. The nucleon is the general term for either a proton or a neutron. Nucleons are formed of three valence quarks embedded in a frothing sea of gluons. Our knowledge of how protons and neutrons are constructed from their quark and gluon constituents, however, is rudimentary at best. An energetic particle, such as an electron, incident on a nucleon can interact directly with one of the valence quarks inside, causing the quark to undergo a flip in spin or endowing the quark with an orbital or radial excitation. With a quark in a higher energy state, the excited nucleon becomes more massive. These excited states are called nucleon resonances (N*s) and exist for the briefest of moments – on the order of a trillionth of a trillionth of a second (10−24 s), and thence will decay into other particles. The types of particles produced and how they are distributed in space provides key information on the make-up of the proton. Lamar University is a Primarily Undergraduate Institution. Over the course of the past two decades, the PI has established a strong record of involving undergraduate students in his research program, and that practice will continue with support from this award. These fundamental measurements on understanding nucleon resonances at Jefferson Lab (Newport News, Virginia) and at ELSA (Bonn, Germany), along with the strong educational focus of this award, are in keeping with the key objectives of the Nuclear Science Advisory Committee’s 2015 Long-Range Plan and thereby serve the national interest.This research program is a study of the fundamental properties and structure of nucleons by using a beam of linearly-polarized photons and/or polarized electrons at Jefferson Lab and at ELSA. The strong nuclear interaction is responsible for phenomena over a large distance scale from the binding of quarks by gluons, the combinations of quarks into colorless hadrons, the binding of nucleons into nuclei, and the collective behavior of large nuclei. This research group seeks answers to questions such as how valence quarks self-assemble when sea quark and gluon contributions are minimal, the nature of how gluons attach to quarks to increase the mass of current quarks to that of constituent quarks, and how quarks resonate inside the nucleon to form excited assemblies of quarks. The PI and his group of undergraduate students aim to understand the emergent behavior and structure from assemblies of quarks and gluons. The probe for these studies will be the omega meson. There is great discovery potential in probing the structure of N*s through the clean and unambiguous signal of the omega meson. Moreover, there is a significant dearth of data of baryon resonances decaying through the omega mode as a function of momentum transfer.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.