Probing electromagnetic structure of the nucleon using polarization at Jefferson lab

杰斐逊实验室利用极化探测核子的电磁结构

• 批准号: 238383-2009
• 负责人: Sarty, Adam
• 金额: $ 2.4万
• 依托单位: Saint Mary's University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2009
• 资助国家: 加拿大
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=425508
• 关键词: Probing; electromagnetic; structure; nucleon; using

During the past century, a revolution has occurred in the understanding of the structure of matter. We have moved well into examination of the myriad of complexity contained inside atoms - proposed as "indivisible" in 1805 by Dalton - from molecular structures, to electron orbitals around a nuclear center, to the structure of the atomic nucleus itself. In 1932, the discovery of the neutron brought acceptance to the idea that the atomic nucleus is composed of elementary particles called neutrons and protons (or "nucleons"); further, during the 1970's, experimental results made it clear that even these nucleons are individually made of more fundamental particles called quarks and gluons. Modern nuclear physics researchers now strive to gain clear insight into understanding the interactions between these underlying quarks and gluons, and how these interactions give rise to the internal structure properties of nucleons. While a very good theoretical framework (called Quantum Chromo Dynammics, or QCD) exists which can accurately describe how quarks and gluons interact at extremely high energies (or, equivalently, when the quarks are very close together), an unfortunate reality is that this theory of QCD is very difficult to solve/interpret at lower energies (or, at larger distances) because the quark/gluon force gets increasingly complicated as they get further apart. However, this complicated interaction of quarks and gluons is manifest by the rich structure which nucleons have been measured to possess; while it's clear such nucleon structure results from the motion of its internal electrically-charged quarks, the exact connection of the observed low-energy structure of nucleons to the underlying theory of QCD remains one of the central problems of modern physics research. This research proposal will exploit the existing 6-billion-Volt electron beam at Jefferson Laboratory in the USA to make precision measurements of low-energy proton structure, as well as contribute to designing/constructing new scintillating-fiber tracking detectors to be used in studies to push these proton structure measurements up in energy as Jefferson Lab enters a construction phase to increase its electron beam energy to 12-billion-Volts.

在过去的一个世纪中，对物质结构的理解发生了一场革命。 我们已经深入研究原子内部包含的无数复杂性——道尔顿于 1805 年提出“不可分割”——从分子结构到核中心周围的电子轨道，再到原子核本身的结构。 1932 年，中子的发现使人们接受了原子核由称为中子和质子（或“核子”）的基本粒子组成的观点；此外，在 20 世纪 70 年代，实验结果清楚地表明，即使是这些核子也是由更基本的粒子（称为夸克和胶子）单独构成的。 现代核物理研究人员现在努力清楚地了解这些底层夸克和胶子之间的相互作用，以及这些相互作用如何产生核子的内部结构特性。 虽然存在一个非常好的理论框架（称为量子色动力学，或 QCD），可以准确地描述夸克和胶子如何在极高能量下（或者等效地，当夸克非常接近时）相互作用，但不幸的现实是该理论QCD 的问题在较低能量（或在较大距离）下很难解决/解释，因为夸克/胶子力随着它们距离越来越远而变得越来越复杂。 然而，夸克和胶子的这种复杂的相互作用通过测量核子所具有的丰富结构而得到体现。虽然很明显这种核子结构是其内部带电夸克运动的结果，但观察到的核子低能结构与 QCD 基础理论的确切联系仍然是现代物理学研究的核心问题之一。 该研究计划将利用美国杰斐逊实验室现有的 60 亿伏电子束对低能质子结构进行精确测量，并有助于设计/构建用于研究的新型闪烁光纤跟踪探测器随着杰斐逊实验室进入建设阶段，将其电子束能量增加到 120 亿伏，将这些质子结构测量的能量推高。