Investigation of Nuclear Structure with Intermediate Energy Photons

美国天主教大学(CUA)的研究小组将主要利用托马斯·杰斐逊国家加速器设施(JLab)B厅的仪器，研究核子结构以及夸克在确定这种结构中的作用。这项工作中的一个基本工具是光子标记器--一种测量光子入射能量的设备，该设备随后会产生对核目标感兴趣的反应。然后，通常由CEBAF大接受光谱仪(CLAS)收集和分析反应产物，以便提取有关所涉及的核相互作用的感兴趣的基本信息。CUA小组主要负责标记器的设计、建造和调试，B厅大约40%的实验都使用了标记器。除了对B厅的持续承诺外，我们已经开始为新的D厅设计标记器--JLab升级到更高能量的拟议组件。作为CLAS合作的创始成员，CUA小组将继续参与大多数使用标记器的实验的数据获取和分析活动。我们特别感兴趣的一项研究是K介子和超子的光产生，以提高对奇怪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，这是中国大学一名博士生的论文项目。我们正在完善一项研究Gerasimov-Drell-Hain求和规则的贡献的提案，该规则与质子的最基本性质有关。除了与CLAS的合作，我们也是另外两个使用标记器而不使用Clas探测器的项目的合作伙伴--测量Phi介子的罕见衰变，以及即将使用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.