Double Polarization Experiments With Gamma Rays

这项提案寻求支持，以完成数据采集，并开始分析布鲁克海文国家实验室LEGS(激光电子伽马源)设施的双极化实验数据。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对激光的后向散射，产生覆盖(3，3)共振能区的偏振伽马射线。研制了一种新型的固体氢-氚极化靶--SPHICE。之前研究中性介子产生的数据都是超干净的。最终数据将使用时间投影室、大口径螺线管磁体和围绕目标的专用触发探测器(后者由弗吉尼亚理工大学建造)完成带电粒子终态实验。在LEGS设备上获取的数据可以解决核子结构中的一些最重要的问题，例如，可以同时测试中子和质子的GDH求和规则。这将导致改进的核子自旋结构模型。同时，由于可以同时测量多个双偏振振幅和通道，因此可以计算出一套完整的π介子光生振幅。

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.