Double Polarization Experiments With Gamma Rays

本提案寻求支持完成数据采集并开始分析布鲁克海文国家实验室LEGS（激光电子伽玛源）设备的双极化实验数据。LEGS是一个独特的核物理实验室。它通过在存储环中循环的相对论电子的激光反向散射，产生覆盖（3,3）共振能区的偏振伽马射线。提出了一种新型的固体氢氘极化靶SPHICE。以前研究中性介子产生的数据是超干净的。最终数据将完成带电粒子最终状态实验，使用时间投影室、大口径电磁磁铁和目标周围的专用触发探测器（后者由弗吉尼亚理工大学建造）。在LEGS设施中收集的数据可以解决核子结构中一些最重要的问题，例如，可以对中子和质子进行GDH和规则的测试。这将导致一个改进的核子自旋结构模型。由于可以同时测量多个双偏振幅值和通道，因此可以计算出一套完整的介子光产生幅值。

This proposal seeks support to finish data taking and begin analysis of the data from the double polarization experiments at the LEGS (Laser Electron Gamma Source) facility at Brookhaven National Laboratory. LEGS is a unique nuclear physics laboratory. It creates polarized gamma rays covering the (3,3) resonance energy region via back scattering of laser light from relativistic electrons that circulate in a storage ring. A novel polarized target of solid Hydrogen-Deuterium, SPHICE, has been developed. Previous data that studied neutral pion production are ultra clean. The final data will complete the charged particle final state experiments using a time projection chamber, large bore solenoidal magnet, and dedicated trigger detectors surrounding the target (the latter built by Virginia Tech). Data taken at the LEGS facility can address some of the most important problems in the structure of the nucleon, for example, the GDH sum rule can be tested for both neutrons and protons. This will lead to an improved model of nucleon spin structure. Also because many double polarization amplitudes and channels can be simultaneously measured, a complete set of pion-photo-production amplitudes can be worked out.