Precision Moller Polarimetry for Electroweak Scattering Experiments

众所周知，原子核是由质子和中子组成的。在重核中，中子比质子多，这导致了理论上的预测，即重核有一层中子的外壳。对重原子核中中子过剩的测量也适用于天体物理学，在天体物理学中，已知存在被称为中子星的物体。重核的中子皮厚度直接影响中子物质的理论计算，从而影响中子星的组成。这一奖项将支持一项实验的研究，该实验将直接测量目前鲜为人知的中子皮厚度，具有足够高的精度，可以测试不同的中子物质理论模型。这项研究的很大一部分将涉及坦普尔大学社区的本科生，同时还将进行一项招聘工作，以吸引希望留在该市担任科学教师的学生。这项实验依赖于来自多所大学的物理学家以及托马斯·杰斐逊国家加速器设施的大量合作。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极化的具体努力。这是在一种束流设置或另一种束流设置下，自旋指向一个方向而不是另一个方向的电子的比例。我们的目标是确定偏振到大约1%的精度，这需要仔细注意一些不同的细节。例如，这项技术涉及在强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.