A Program of Measurements of High Energy Electron and Gamma Ray Interactions With Matter

9971942 Arnold该提案要求支持美国大学集团（主要在斯坦福大学直线加速器中心）准备、实施和分析一系列物质电磁结构的测量。 这项工作的共同点是使用高能（有时是极化的）电子和伽马射线来探测物质和宇宙。 这项工作将在三个主要领域进行。 主要工作是完成E155和E155 x实验的数据分析和出版，以测量极化质子和中子靶的极化深非弹性电子散射，以提取核子中的夸克和胶子自旋分布。 SLAC电子束的高强度和高极化以及稳健和高度极化的目标使得精确测量自旋不对称性成为可能，这些自旋不对称性提供了关于核子质子结构的独特和重要信息。精确的测量使QCD理论的严格测试成为可能，通过与自旋结构的次领先阶计算的比较，基本Bjorken求和规则的评估，以及在低动量转移时强耦合常数的提取。 另一个主要的工作领域将是为实验E158的数据运行做准备，实验E158使用高强度极化电子束来测量电子-电子散射中违反宇称的不对称性。 这一高精度的数据将提供重要的测试标准模型在低动量转移的电子磁耦合通过交换虚光子和Z玻色子之间的干扰。美国大学集团将为磁谱仪、数据采集系统和谱仪校准离子系统的设计和实施做出贡献。第三个工作领域将是协助开发伽马射线大面积空间望远镜GLAST的探测器系统，这是一个国际项目，提议在伽马射线天体物理学测量卫星上发射新一代大接受度伽马射线观测站。美国大学集团加入了GLAST合作，并将组织和帮助进行原型的广泛校准，并最终在SLAC的电子和伽马射线束中进行完整的探测器。

9971942ArnoldThis proposal requests support for preparing, carrying out, and analyzing a series of measurements of electromagnetic structure of matter by the American University Group, primarily at the Stanford Linear Accelerator Center. This work has as a common t hread the use of high energy (sometimes polarized) electrons and gamma rays to probe matter and the universe. The work will be in three main areas. The major work will be the completion of data analysis and publications for Experiments E155 and E155x t o measure polarized deep inelastic electron scattering from polarized proton and neutron targets to extract the quark and gluon spin distributions in the nucleons. The high intensity and high polarization of the SLAC electron beam together with robust and highly polarized targets makes possible precise measurements of the spin asymmetries that provide unique and important information on the proton structure of the nucleons. Precise measurements make possible stringent tests of QCD theory from comparisons with next-to-leading-order calculations of spin structure, evaluation of the fundamental Bjorken sum rule, and extraction of the strong coupling constant at low momentum transfer. Another major area of work will be the preparation for the data run for experiment E158 using the high intensity polarized electron beam to measure parity violating asymmetry in electron-electron scattering. This high precision data will provide important tests of the Standard Model at low momentum transfer in the electron magnetic coupling via the interference between exchange of virtual photons and Z bosons. The American University Group will contribute to the design and implementation of the magnetic spectrometers, data acquisition system, and to the spectrometer calibrate ion systems. The third area of work will be to contribute to the development of the detector systems for GLAST, the Gamma Ray Large Area Space Telescope, an international project that proposes to launch a new generation large acceptance gamma ray observatory in a satellite forgamma ray astrophysics measurements. The American University Group has joined the GLAST collaboration and will organize and help conduct the extensive calibrations of the prototype and eventually the full detector in the electron and gamma ray beams at SLAC.