Precision Moller Polarimetry for Electroweak Scattering Experiments

众所周知，原子核是由质子和中子构成的。在重核中，中子比质子多，这就产生了一种理论预测，即重核有一层中子的“外皮”。对重核中多余中子的测量也应用于天体物理学，在天体物理学中已知存在中子星。重核中子皮的厚度直接关系到中子物质的理论计算，从而关系到中子星的组成。该奖项将支持一项实验的研究，该实验将直接测量中子表面厚度，这是目前鲜为人知的，具有足够高的精度来测试中子物质的不同理论模型。这项研究的很大一部分将涉及天普大学社区的本科生，同时还有一项招聘工作，旨在吸引希望留在这座城市担任科学教师的学生。这个实验依赖于来自多所大学的物理学家的大规模合作，以及托马斯·杰斐逊国家加速器设施。每个小组都为成功的测量发挥了自己的作用，该奖项支持精确测量电子束偏振的具体努力。这是给定一种或另一种光束设置的电子的比例，自旋指向一个方向而不是另一个方向。我们的目标是确定偏振的精度约为1%，这需要仔细注意许多不同的细节。例如，该技术涉及在高磁场中精确测定薄铁箔的磁化强度。

It is well known that nuclei are made from protons and neutrons. In heavy nuclei, there are more neutrons than protons, and this gives rise to the theoretical prediction that heavy nuclei have an outer "skin" of neutrons. Measurements of the neutron excess in heavy nuclei also have applications to astrophysics, where objects called neutron stars are known to exist. The thickness of the neutron skin for heavy nuclei bears directly on the theoretical calculations of neutron matter and hence the composition of neutron stars. This award will support research on an experiment that will directly measure the neutron skin thickness, which is poorly known today, with high enough precision to test different theoretical models of neutron matter. A significant fraction of the research will involve undergraduate students from the Temple University community, accompanied by a recruitment effort that seeks to attract students who wish to remain in the city as science teachers. This experiment relies on a large collaboration of physicists from a number of universities, as well as the Thomas Jefferson National Accelerator Facility. Each group plays its part for a successful measurement, and this award supports a specific effort to precisely measure the polarization of the electron beam. This is the fraction of electrons, given one beam setting or another, with spins pointed in one direction as opposed to the other. The goal is to determine the polarization to about 1% accuracy, and this requires careful attention to a number of different details. For example, the technique involves precision determinations of magnetization of thin iron foils in high magnetic fields.