Studies of hadronic structure using electromagnetic probes

使用电磁探针研究强子结构

• 批准号: 105851-2011
• 负责人: Huber, Garth
• 金额: $ 5.46万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=545221
• 关键词: Studies; hadronic; structure; using; electromagnetic

One of the central problems of modern physics concerns our understanding of the building blocks of the atomic nucleus: the nucleons (protons and neutrons), and particles (mesons) that bind them. Notable discoveries have indicated that mesons and nucleons consist of yet more fundamental constituents, the quarks and gluons. As a result of the motion of the quarks (which produces magnetism) and their electrical charge, mesons and nucleons exhibit a distinct structure. While a very good theoretical framework (called Quantum ChromoDynamics, or QCD) is able to accurately describe how quarks and gluons interact at extremely high energies (or, equivalently, when the quarks are very close together), it has been extremely difficult to apply QCD to lower energy (larger distance) phenomena. The paradox is that the increasing complexity of the quark-gluon interaction as quarks get further apart is critically important to their confinement within mesons and nucleons, but this complexity greatly limits our ability to perform the QCD calculations needed to confirm our understanding. One of the obstacles to our improved comprehension has been a lack of quality data, particularly for the Deep Exclusive electron scattering reactions where the system responds coherently to the incoming probe, and so provides the clearest picture of the inner workings of QCD. These measurements are technically challenging and only now are made feasible with recent advances in accelerator and detector technology, as enabled by the ongoing upgrade of Jefferson Lab Hall C. Dr. Huber leads several experiments, such as Measurements of the Charged Pion Form Factor and QCD Factorization Studies of Exclusive pi+ and K+ Production, which show particular promise to our understanding of the underlying quark/gluon dynamics and provide valuable input to the interpretation of other experiments. By making precision measurements of this nature, we hope to better understand the short-long range transition of QCD, and better make the elusive connection between the underlying quark/gluon dynamics and the observed structures of mesons and nucleons.

现代物理学的核心问题之一涉及到我们对原子核的组成部分的理解：核子(质子和中子)，以及束缚它们的粒子(介子)。值得注意的发现表明，介子和核子由更基本的成分夸克和胶子组成。由于夸克(产生磁性)及其电荷的运动，介子和核子呈现出不同的结构。虽然一个非常好的理论框架(称为量子色动力学，或QCD)能够准确地描述夸克和胶子在极高能量下(或相当于当夸克非常接近时)如何相互作用，但将QCD应用于较低能量(较大距离)的现象一直是极其困难的。自相矛盾的是，随着夸克之间的距离越来越远，夸克-胶子相互作用的复杂性对它们被限制在介子和核子中至关重要，但这种复杂性极大地限制了我们进行QCD计算的能力，而QCD计算是确认我们的理解所需的。我们提高理解的障碍之一是缺乏高质量的数据，特别是对于深度独占电子散射反应，在这种反应中，系统对传入的探测器做出一致的响应，因此提供了QCD内部工作原理的最清晰图像。这些测量在技术上具有挑战性，而且直到现在才得以实现，因为杰斐逊实验室大厅C的持续升级使加速器和探测器技术的最新进展成为可能。Huber博士领导了几个实验，例如测量带电的Pion形状因子和QCD因式分解研究，这些实验对我们理解潜在的夸克/胶子动力学特别有希望，并为解释其他实验提供了宝贵的信息。通过这种性质的精确测量，我们希望更好地理解QCD的短程-长程跃迁，并更好地将潜在的夸克/胶子动力学与观察到的介子和核子结构之间的难以捉摸的联系联系起来。