Polarized Electron Scattering from Nucleons

这项研究拨款支持一项电磁和弱电流实验计划，以探索质子和中子(核子)的味道含量和自旋结构。目前，核子的这些性质还不能用量子色动力学这一公认的强相互作用基本理论来精确预测，因此实验必须走在前列。在托马斯·杰斐逊国家加速器设施(杰斐逊实验室)进行的一系列违反宇称的电子散射实验将使我们能够确定奇怪夸克对核子基态的贡献。这些实验包括在Halla测量动量转移时质子散射中违反宇称的不对称性，以及测量4He和208Pb的散射中的不对称性。C厅的G0宇称破坏实验正在从设计和施工阶段进入调试和数据采集阶段。这个实验将明确地描绘出核子的奇异夸克矢量形状因子作为动量转移的函数。对N到Delta(1232)跃迁的不对称性的测量将同时进行，而对氘的计划测量将探测轴向形状因数。正在开发一项新的举措，使用G0光谱仪的改进型，在极低的动量转移下进行宇称破坏电子散射实验，以便对标准模型以外的物理现象进行灵敏的研究。杰斐逊实验室的一系列极化电子散射实验致力于利用极化3Hetarts来阐明核子的自旋结构。这项计划正在进行中，明年将在杰斐逊实验室进行三项使用这些目标的实验，威廉和玛丽的3Hetarget细胞实验室支持这一计划。

This research grant supports a program of electromagnetic and weakcurrent experiments to probe the flavor content and spin structure of protons and neutrons(nucleons). At present, these properties of the nucleon cannot beprecisely predicted using quantum chromodynamics, the acceptedfundamental theory of the strong interaction, and so experiment mustlead the way. A series of parity-violating electron scattering experiments at theThomas Jefferson National Accelerator Facility (Jefferson Lab) willenable us to determine the strange quark "sea" contribution to thenucleon ground state. These experiments include a measurement in HallA of the parity-violating asymmetry in scattering from the proton atlow momentum transfer, and measurements of the asymmetry in scatteringfrom 4He and 208Pb. The G0 parity-violation experiment in Hall C ismoving from the design and construction stage to the commissioning anddata-taking stage. This experiment will definitively map out thestrange quark vector form factors for the nucleon as a function ofmomentum transfer. A measurement of the asymmetry for the N toDelta(1232) transition will be made simultaneously, and plannedmeasurements on deuterium will probe the axial form factor. A new initiative is under development to use a modified version of the G0 spectrometer to perform a parity-violation electron scattering experiment at very low momentum transfer, in order to make a sensitivesearch for physics beyond the standard model. A series of polarizedelectron scattering experiments at Jefferson Lab are dedicated toelucidating the spin structure of the nucleon using polarized 3Hetargets. This program is well underway, three experiments using thesetargets will take place in the next year at Jefferson Lab, and a 3Hetarget cell lab at William and Mary supports this program.