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

本研究利用光子散射和介子产生，利用偏振光束和靶研究核子和核子共振的性质。实验项目位于杜克大学杜克自由电子激光实验室的高强度伽玛源（HIGS）设施，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）。HIGS设施为通过来自极化和非极化核子和核目标的伽马射线的弹性散射研究核子结构打开了一扇新的窗口。这个程序将测量原子核对伽马射线波动的电场和磁场的响应特征。这些数据将允许对有效场论进行精确测试，对强相互作用进行数值计算，以及对粒子物理标准模型进行计算和预测。JMU正在与HIGS合作者合作，建立一个理想的低能光子散射实验的主动极化质子靶。虽然JLab批准的实验使用正在开发的极化丁醇靶标将限制介子光产生的拟合，但这些实验本身是不够的。利用CEBAF大接受谱仪（CLAS）在强极化HD冰（SPHICE）靶中同时测量了五个介子产生通道的极化中子的束靶不对称性。这将提供第一个伪标量介子光产生振幅的（超）测定，并将摆脱困扰该领域数十年的模糊性。该实验E06-101于2006年8月进行了审查，被批准为“A”级，并分配了整个波束时间请求。虽然冷冻自旋高清目标SPHICE是用于二次光束的理想选择，但要在主光束中使用该目标，要么必须证明光束的去极化效应很小，要么必须找到新的操作方法。JMU小组将与来自UVA的合作者一起研究操作动态极化高清目标的可能性。目标照射将在NIST使用在JMU蒸馏的高纯度HD的医疗-工业辐射设备进行。具有高极化特性的动态极化高清目标是极化目标技术的重要进展。JMU的本科生将参与校内和校外的活动。校园活动将包括用于SPHICE目标的HD蒸馏，偏振闪烁靶材料制造和NaI探测器组装和测试，以及高年级学生的数据分析。这些活动促进了该系各个研究小组之间的联系，为JMU新的核物理实验室的持续发展奠定了基础，并允许扩大新的外展活动。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，并使他们接触到被这些设施吸引的光子核物理专家。JMU科学与数学学院目前有四个NSF REU项目资助（材料、化学、生物和数学）。这些项目合作产生了一个充满活力的暑期研究社区。这里概述的项目将带回校外经验，不仅丰富了该组中更多大三学生的经验，也丰富了REU其他项目的学生的经验。JMU的研究和教学被认为是同一过程的两个方面。这种研究和教育的结合一直是JMU高评价的本科体验的标志之一。

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.