RUI: The Study of Intermediate Energy Photonuclear Physics with Polarized Beams and Targets

这项研究使用光子散射和介子产生来研究核子和核子共振的性质，并使用偏振光束和靶子。该实验计划位于杜克大学杜克自由电子激光实验室、弗吉尼亚州纽波特纽斯的杰斐逊实验室(JLab)和马里兰州盖瑟斯堡的国家标准与技术研究所(NIST)的高强度伽马源(HIGS)设施中。HIGS设施为通过对极化和非极化核子和核靶的伽马射线进行弹性散射来研究核子结构打开了一扇新的窗口。这个计划将测量表征核子对伽马射线波动电场和磁场的响应的量。这些数据将用于有效场理论的精确测试、强相互作用的数值计算以及粒子物理标准模型的计算和预测。JMU正在与HIGS的合作者合作，建立一种活跃的极化质子目标，非常适合在低能量下进行光子散射实验。尽管JLab批准的使用正在开发的极化丁醇目标的实验将限制对介子光产生的适应，但这些实验本身是不够的。利用CEBAF大接受能谱仪(CLAS)联合测量了强极化HD冰(SPHICE)靶中5个介子产生通道和极化中子的束靶不对称性。这将首次(过度)确定伪标量介子的光产生幅度，并将摆脱困扰该领域数十年的模棱两可的问题。这项实验，E06-101，于2006年8月被审查，被批准为“a”级，并分配了整个光束时间要求。尽管冻结的自旋HD靶SPHICE是用于二次光束的理想对象，但要在主光束中使用该靶，要么必须证明光束的去偏振效应很小，要么必须找到新的操作方法。JMU小组将与UVA的合作者一起，研究操作动态极化高清目标的可能性。目标辐射将在NIST使用医疗-工业辐射设备在JMU蒸馏的高纯度HD上进行。高极化的动态高清靶标将代表着偏振靶标技术的重大进步。JMU本科生将参与校园内外的活动。校内活动将包括用于SPHICE靶材的HD蒸馏、可极化闪烁体靶材制作和NaI探测器组装和测试，对于更高年级的学生，将进行数据分析。这些活动促进了系内各研究小组之间的联系，构成了继续发展联合监测大学新的核物理实验室的基础，并使新的外联举措得以扩大。校外工作将向学生介绍在最先进的设施中完成的“大型”物理，并将他们介绍给被这些设施吸引的光核物理专家。JMU的科学和数学学院目前有四个由NSF资助的REU项目(材料、化学、生物和数学)。这些项目共同造就了整个学院充满活力的暑期研究社区。这里概述的项目将带回校外体验，不仅丰富这一组中更多低年级学生的体验，也将丰富其他REU项目中的学生的体验。JMU的研究和教学被认为是同一过程的两个方面。这种研究和教育的融合仍然是JMU高度评价的本科生经历的标志之一。

The proposed research uses photon scattering and meson production to investigate the properties of the nucleon and nucleon resonances using polarized beams and targets. The experimental program is located at the High Intensity Gamma Source (HIGS) facility at the Duke Free Electron Laser Laboratory laboratory at Duke University, Jefferson Laboratory (JLab) in Newport News, VA and the National Institute for Standards and Techonology (NIST) in Gaithersburg, MD.The HIGS facility opens a new window to the study of nucleon structure through elastic scattering of gamma-rays from both polarized and unpolarized nucleon and nuclear targets. This program will measure quantities that chacterize the response of the nucleon to the fluctuating electric and magnetic fields of the gamma-rays. This data will allow for precision tests of effective field theories, numerical calculations of the strong interaction as well as calculations and predictions of the standard model of particle physics. JMU is working with HIGS collaborators to build an active polarized proton target ideal for photon scattering experiments at low energies.Although approved experiments at JLab using a polarized butanol target now under development will constrain fits to meson photoproduction, these experiments alone are insufficient. A collaboration has been assembled to measure beam-target asymmetries for five meson production channels simultaneously with polarized neutrons in the Strongly Polarized HD Ice (SPHICE) target using the CEBAF Large Acceptance Spectrometer (CLAS). This will provide the first (over-)determination of a pseudoscalar meson photo-production amplitude and will be free of the ambiguities that have plagued this field for decades. This experiment, E06-101, was reviewed in August 2006, was approved with an ``A'' rating and alloted the entire beam-time request.Although the frozen spin HD target, SPHICE, is ideal for use in secondary beams, to use the target in a primary beam either the depolarizing effects of beam must be demonstrated to be small or new methods of operation must be found. The JMU group will, with collaborators from UVA, investigate the possibility of operating a dynamically polarized HD target. Target irradiation will be done at NIST using the Medical-Industrial Radiation Facility on high purity HD distilled at JMU. A dynamically polarized HD target with a high polarization would represent a significant advance in polarized target technology.JMU undergraduate students will be involved in both on- and -off campus activities. The on-campus activities will include distillation of HD for SPHICE targets, polarizable scintillator target material fabrication and NaI detector assembly and testing, and for the more senior students, data analysis. These activities foster connections among the various research groups in the department, form the basis for the continued development of a new nuclear physics lab at JMU and allow the expansion of new outreach initiatives. The off-campus work will introduce the students to ``large'' physics done at state-of-the-art facilities and expose them to the experts in photonuclear physics that are attracted to these facilities. The College of Science and Mathematics at JMU currently has four NSF REU programs funded (Materials, Chemistry, Biology and Mathematics). These programs cooperatively produce a vibrant summer research community spanning the college. The program outlined here will bring off-campus experiences back to enrich the experience of not only the more junior students in this group but also those in the other REU programs. Research and teaching at JMU are recognized as two facets of the same process. This integration of research and education continues to be one of the hallmarks of the highly rated undergraduate experience at JMU.