Precision Electroweak Studies of the Standard Model

这个为期2年的桥梁项目将支持新聘请的PI （Deconinck）对标准模型进行三次精确的电弱测量，标准模型是我们目前描述基本粒子及其相互作用的最佳理论。这个桥梁项目将确保一个正在进行的SAP项目（MOLLER）和两个未来的SAP项目（BL3和EIC EW）的研究连续性，同时建立一个加拿大社区。所有三个项目都将在两年内过渡到亚原子物理信封-项目支持：MOLLER将进入正在进行的SAP项目，该项目将于2021年更新，BL3和EIC EW将进入新项目。将精确测量得到的参数与理论预测进行比较，可以对标准模型进行精确测试。这个桥梁项目侧重于三种方法。1) PI和1名博士生将为杰斐逊实验室的MOLLER实验设计、建造和测试介子探测器系统，这是对电子弱电荷的精确测量。MOLLER实验将测量液氢靶中纵向极化电子与非极化电子散射时的奇偶违反不对称性。不对称测量的背景是光产生的介子。我们将在主要的MOLLER探测器之后添加一个铅吸收器，以排除大部分电子，但让很大一部分介子通过。铅墙后面是丙烯酸切伦科夫探测器，由光倍增管读出。一名博士生将设计、建造和测试丙烯酸切伦科夫探测器的概念。2) PI和1名博士生将模拟和测试NIST BL3精密中子寿命实验的质子探测器。自20世纪90年代以来，使用两种实验技术（瓶实验和束实验）测量中子寿命之间一直存在差异。BL3实验旨在将过去“光束”实验2.1 s的不确定性提高到0.3 s以上。为了探测衰变质子，实验将使用一个分段硅探测器。一名博士生将模拟质子在分段硅探测器上的反向散射，并在我们的质谱仪设备上测试它们的性能。3) PI和1名共享博士后将使用JLab已经开发的分布式仿真平台，完成电子-离子对撞机（EIC）的电弱精度测量研究。EIC是核物理学界备受瞩目的研究成果之一。该设备将允许对中性电流电弱观测物进行精确测量。作为EIC软件联盟的一部分，我们已经开发了一个分布式仿真工作流程，因此可以很好地利用新的探测器设计重新审视通用仿真。以半名博士后的时间，更新基于EIC探测器系统的电弱混合角和形状因子提取的研究。所有这三个组成部分确保了亚原子物理计划相关领域的高素质人员的培训。

This 2-year bridge program will support the newly-hired PI (Deconinck) on three precision electroweak measurements of the Standard Model, our current best theory describing fundamental particles and their interactions. This bridge program will ensure research continuity in one ongoing SAP project (MOLLER) and in two future SAP projects (BL3 and EIC EW) while building a Canadian community. All three projects will transition to Subatomic Physics Envelope - Project support within 2 years: MOLLER onto the ongoing SAP project which will be due for renewal in 2021, and BL3 and EIC EW onto new projects. The comparison of parameters determined from precision measurements with theoretical predictions allow for precision tests of the Standard Model. This bridge program focuses on three approaches. 1) The PI and 1 PhD student will design, build, and test the pion detector system for the MOLLER experiment at Jefferson Lab, a precision measurement of the electron's weak charge. The MOLLER experiment will measure the parity-violating asymmetry in the scattering of longitudinally-polarized electrons from unpolarized electrons in a liquid hydrogen target. A background for the asymmetry measurement is photo-produced pions. We will add a lead absorber after the main MOLLER detectors to range out most of the electrons but letting through a large fraction of the pions. Behind this lead wall will be acrylic Cherenkov detectors read out by photo-multiplier tubes. One PhD student will design, build, and test the acrylic Cherenkov detector concept. 2) The PI and 1 PhD student will simulate and test the proton detectors for the BL3 precision neutron lifetime experiment at NIST. Since the 1990s there has been a persistent discrepancy between the neutron lifetime measurements using two experimental techniques: bottle and beam experiments. The BL3 experiment aims to improve the 2.1 s uncertainty of the past "beam" experiments to better than 0.3 s. To detect decay protons, the experiment will use a segmented silicon detector. One PhD student will simulate backscatter of protons on the segmented silicon detectors, and test their performance in our mass-spectrometer facility. 3) The PI and 1 shared postdoc will complete studies for electroweak precision measurements at the Electron-Ion Collider (EIC), using distributed simulation platforms already developed at JLab. One of the high profile efforts in nuclear physics is the EIC. This facility will allow for precise measurements of neutral-current electroweak observables. We have developed a distributed simulation workflow as part of the EIC software consortium, and thus well positioned to revisit generic simulations with new detector designs. With half of one postdoc, we will update studies of the electroweak mixing angle and form factor extractions based on the detector systems designed for the EIC. All three components ensure training of highly qualified personnel in areas relevant to the subatomic physics program.