Measurement of a Lepton Lepton Electroweak Reaction (MOLLER): An Ultraprecise Measurement of the Weak Mixing Angle using Moller Scattering at Jefferson Laboratory

轻子轻子电弱反应 (MOLLER) 的测量：杰斐逊实验室使用莫勒散射对弱混合角进行超精确测量

• 批准号: SAPPJ-2017-00042
• 负责人: Mammei, Juliette
• 金额: $ 11.8万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=658616
• 关键词: Measurement; Lepton; Electroweak; Reaction; MOLLER

The discovery of the Higgs boson at CERN was the long-awaited validation of the Standard Model, which summarizes our current understanding of fundamental particles and their interactions. The four fundamental forces are the gravitational, electromagnetic, weak and strong nuclear forces. Ordinary matter consists of a subset of the fundamental particles, electrons and up- and down- quarks bound together as protons and neutrons in the nucleus. The electromagnetic and weak forces have been successfully unified into a quantum electroweak theory, and it is a goal of subatomic theorists to unify the other two forces as well. Despite the success of the Standard Model, it is not complete. Approximately 97% of the matter and energy in the universe is unknown; this "dark" matter and energy is needed to explain the rotation rates of galaxies from astrophysical observations, but is not yet included in the Standard Model. In addition, the two most precise measurements of the weak mixing angle at the mass of the Z boson, which is the mediator of the weak force, do not agree with each other or the measured mass of the Higgs.******The MOLLER collaboration will measure the parity-violating asymmetry in polarized electron-electron (Moller) scattering in order to make an ultra-precise measurement of the weak mixing angle. This is a quantity with a definite prediction in the Standard Model and due to the precision of the measurement any deviation from the predicted value is a sign of new physics. The asymmetry arises due to the interference of scattering via a photon (mediator of the electromagnetic force) and a Z boson. This asymmetry is expected to be on the order of 35 parts per billion (ppb), and the collaboration will measure it to within 0.73 ppb, a fractional accuracy of about 2%. The measurement will be carried out in Hall A of Jefferson Lab, using 11 GeV longitudinally polarized electrons incident on a 1.5 m liquid hydrogen target. Atoroidal spectrometer will be used to separate the Moller electrons from those which scatter from the protons in the hydrogen, and focus them at the detector plane 28 m downstream of the target. The integrated yield of the scattered electrons will be measured by an array of 224 quartz Cherenkov detectors.******The MOLLER experiment will be as good as either of the two most precise measurements of the weak mixing angle made at colliders, and will help to resolve the discrepancy with the Higgs mass. It serves as a complement to direct searches for new physics at high energy colliders. Due to its precision MOLLER has discovery potential for physics beyond the Standard Model with contact interaction scales well over 10 TeV, a level of sensitivity which will not be accessible, even at colliders, for the next decade.

欧洲核子研究中心希格斯玻色子的发现是人们期待已久的对标准模型的验证，它总结了我们目前对基本粒子及其相互作用的理解。四种基本力是引力、电磁力、弱核力和强核力。普通物质由基本粒子的一个子集组成，电子和上下夸克在原子核中以质子和中子的形式结合在一起。电磁力和弱力已经成功地统一到量子电弱理论中，亚原子理论家的目标是统一其他两种力。尽管标准模型取得了成功，但它并不完整。宇宙中大约97%的物质和能量是未知的；这种“暗”物质和能量是解释天体物理观测中星系旋转速率所必需的，但尚未包括在标准模型中。此外，对弱力介质Z玻色子质量的弱混合角的两个最精确测量结果也与希格斯玻色子的测量结果不一致。****** MOLLER合作将测量极化电子-电子（MOLLER）散射中的奇偶违反不对称性，以便对弱混合角进行超精确测量。这是一个在标准模型中有明确预测的量，由于测量的精度，任何与预测值的偏差都是新物理学的标志。这种不对称性是由于光子（电磁力的介质）和Z玻色子散射的干扰而产生的。这种不对称预计在十亿分之35 （ppb）的数量级上，合作将测量到0.73 ppb以内，精度约为2%。测量将在杰弗逊实验室的A厅进行，使用11gev的纵向极化电子入射到1.5 m的液氢靶上。环形谱仪将用于将Moller电子与氢中质子散射的电子分离，并将它们聚焦在目标下游28米的探测器平面上。散射电子的积分产率将由224个石英切伦科夫探测器阵列测量。****** MOLLER实验将与对撞机中对弱混合角进行的两个最精确测量中的任何一个一样好，并将有助于解决与希格斯质量的差异。它可以作为在高能对撞机上直接搜索新物理的补充。由于它的精度，MOLLER有发现超越标准模型的物理的潜力，接触相互作用的尺度远远超过10 TeV，这是一个灵敏度水平，即使在对撞机上，在未来十年也无法达到。