Studies of hadronic structure using electromagnetic probes

使用电磁探针研究强子结构

• 批准号: SAPIN-2016-00031
• 负责人: Huber, Garth
• 金额: $ 8.01万
• 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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=654026
• 关键词: Studies; hadronic; structure; using; electromagnetic

One of the central problems of modern physics research concerns our understanding of the building blocks of the atomic nucleus -- the protons, neutrons, and other particles (mesons) that bind them. Notable discoveries have indicated that these particles consist of yet more fundamental constituents, the quarks and gluons. While a very good theoretical framework (called Quantum Chromo-Dynamics, or QCD) is able to describe accurately how quarks and gluons interact at extremely high energies (or, equivalently, when the quarks are very close together), it has been very difficult to apply QCD to lower energy (longer distance) phenomena. One of the obstacles to our improved comprehension has been a lack of quality data, particularly for the Deep Exclusive Reactions which provide the clearest picture of the inner workings of QCD. These studies are difficult because they require continuous, high luminosity electron beams, and detectors with good particle identification and reproducible systematics. The Jefferson Lab (JLab) 12 GeV upgrade is intended to address these issues.***The proposed research has four key investigations.****1. The Pion Elastic Form Factor (Fpi): Fpi offers our best hope of directly observing QCD's transition from strong-confinement at long-distance scales to asymptotic-freedom at short-distances. Our first objective is to establish the reliability of the extraction of the pion form factor from pi+ electroproduction data over a broad kinematic range. Our second objective is to obtain high quality Fpi measurements from Q2=0.3 to 6.0 GeV2.****2. The K+ Elastic Form Factor (FK): We will take L/T-separated data for the p(e,e'K+)Lambda and p(e,e'K+)Sigma0 reactions at W>2.5 GeV to search for evidence of scattering from the proton's ``kaon cloud.'' If warranted by the data, we will perform the first-ever extraction of the Q2-dependence of the K+ form factor. The data will also improve our understanding of K+ electroproduction, including the coupling constants needed in nucleon-meson and quark models.******3. QCD Factorization in Deep Exclusive pi± and K+ Electroproduction: If the hard scattering regime is reached, the scattering amplitude must factorize into hard and soft processes. In fact, factorization is a prerequisite for the extraction of Generalized Parton Distribution (GPD) information from Deep Exclusive Reactions, but the kinematic regime where factorization applies is only poorly known for meson production channels. We will measure pi+, pi- and K+ L/T-separated cross sections over a wide kinematic range (up to Q2=9 GeV2) to clarify the bounds of the QCD factorization regime.******4. QCD Factorization in Deep Exclusive Vector Meson Electroproduction: As an extension of the QCD factorization studies, we will also take exclusive rho, omega and phi electroproduction data up to Q2=6 GeV2, to provide a better test of the applicability of collinear factorization.***

现代物理学研究的主要问题之一是我们对原子核核心的构建基础的理解 - 质子，中子和其他绑定它们的颗粒（介子）。著名的发现表明，这些颗粒由更基本的宪法，夸克和麸质组成。尽管一个非常好的理论框架（称为量子铬动力学或QCD）能够准确地描述夸克和麸质如何在极高的能量（或同样，当夸克非常接近时）相互作用，但很难将QCD应用于降低能量（长度距离）现象非常困难。我们改善理解的障碍之一是缺乏质量数据，尤其是对于QCD内部工作最清晰的深刻独家反应而言。这些研究很困难，因为它们需要连续的高光度电子束以及具有良好粒子识别和可重复系统学的探测器。 Jefferson Lab（JLAB）12 GEV升级旨在解决这些问题。****拟议的研究有四项重要的研究。**** 1。 PION弹性外形（FPI）：FPI提供了我们的最大希望，即直接观察QCD从长距离尺度上的强量过渡到短期不对称的自由式。我们的第一个目的是在广泛的运动范围内从PI+电源数据中提取质子外形的可靠性。我们的第二个目标是获得Q2 = 0.3至6.0 GEV2的高质量FPI测量。**** 2。 K+弹性外形（FK）：我们将在p（e，e'k+）lambda和p（e，e'k+）sigma0 sigma0反应的l/t分隔数据中，以寻求从Proton的``kaon cloud''中寻找散射的证据。这些数据还将提高我们对K+电源的理解，包括核梅森和夸克模型中所需的耦合常数。****** 3。 QCD在深度PI±和K+电源中的分解：如果达到硬散射状态，则散射放大器必须分解为硬和软过程。实际上，分解是从深度独家反应中提取普遍的Parton分布（GPD）信息的先决条件，但是在介子生产渠道中，分解应用仅闻名的运动学制度。我们将在宽的运动范围内测量Pi+，PI-和K+ L/T分隔截面（最高Q2 = 9 GEV2），以阐明QCD分解状态的边界。****** 4。 QCD分解深度载体中膜电源生产：作为QCD分解研究的扩展，我们还将将Rho，Omega和Phi电源数据的独家数据提供到Q2 = 6 GEV2，以更好地测试Unialereareareation的适用性。*** *** *** ***