Investigation of Nuclear Structure with Intermediate Energy Photons

美国天主教大学（CUA）小组将研究核子的结构和夸克在确定这种结构中的作用，主要使用托马斯杰斐逊国家加速器设施（JLab） B厅的仪器。这项工作中的一个重要工具是光子标记器——一种测量光子入射能量的装置，该光子随后在核目标中产生感兴趣的反应。然后收集和分析反应产物，通常是通过CEBAF大接受谱仪（CLAS），以提取有关核相互作用的基本信息。CUA小组主要负责标签机的设计、建造和调试，随后B馆约40%的实验使用了该标签机。除了对B馆的持续承诺外，我们已经开始为新的D馆设计标签机——这是JLab升级到更高能量的一个组成部分。作为CLAS协作的创始成员，CUA小组将继续参与使用标记器的大多数实验的数据采集和分析活动。我们特别感兴趣的研究是K介子和超子的光产生，以提高对奇异夸克在核子中的作用的理解。目前的研究包括中性K介子的产生，这是中大博士生的论文项目。我们正在改进一项建议，以研究对格拉西莫夫-德雷尔-赫恩和规则的贡献，这是一个与质子最基本性质有关的量。除了clasas合作项目，我们还合作了另外两个项目，它们使用了标注器而不是CLAS探测器——一个是测量π介子的罕见衰变，另一个是即将使用primakoff效应测量中性介子的寿命。

The Catholic University of America (CUA) group will study thestructure of nucleons and the role of quarks in determining thisstructure, principally using instrumentation in Hall B at TheThomas Jefferson National Accelerator Facility (JLab). An essential toolIn this work is the photon tagger -- a device which measures theIncident energy of a photon that subsequently produces a reaction of interestin a nuclear target. The reaction products are then collected andanalyzed, typically by the CEBAF Large Acceptance Spectrometer(CLAS), in order to extract fundamental information of interestabout the nuclear interactions involved. The CUA group had majorresponsibility for the design, construction and commissioning of the tagger, which has subequently been used by about 40% of the experiments in Hall B. In addition to ongoing commitments to Hall B, we have begun work on a tagger design for the new Hall D -- a component of the proposed upgrade of JLab to higher energy.As founding members of the CLAS Collaboration, the CUA group willcontinue to participate in data-taking and analysis activity for mostexperiments that use the tagger. A study of special interest to us is the photoproduction of K mesons and hyperons in order to improveunderstanding of the role of strange quarks in the nucleon. Currentinvestigations include production of neutral K mesons, the dissertation project fora CUA doctoral student. We are refining a proposal to studycontributions to the Gerasimov-Drell-Hearn sum rule, a quantity related to the most fundamenetal properties of the proton. Apart from the CLAScollaboration, we are partners in two other projects which use the tagger but notthe CLAS detector - a measurement of rare decays of the phi meson, and aforthcoming measurement of the lifetime of the neutral pion using the Primakoffeffect.