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对标准模型期待已久的验证，该模型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、电子以及在原子核中作为质子和中子结合在一起的上夸克和下夸克组成。电磁力和弱力已经成功地统一为量子电弱理论，统一其他两种力是亚原子理论家的目标。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；需要这种“暗”物质和能量来解释天体物理观测中星系的旋转速率，但尚未包含在标准模型中。此外，对作为弱力中介的 Z 玻色子质量处的弱混合角的两个最精确的测量结果彼此不一致，也不与希格斯玻色子的测量质量一致。******莫勒合作将测量极化电子-电子（莫勒）散射中宇称破坏的不对称性，以便对弱混合角进行超精确测量。这是标准模型中具有明确预测的量，并且由于测量的精确性，与预测值的任何偏差都是新物理学的标志。这种不对称性是由于光子（电磁力的媒介）和 Z 玻色子的散射干涉而产生的。这种不对称性预计约为十亿分之 35 (ppb)，此次合作将测量其误差在 0.73 ppb 以内，分数精度约为 2%。测量将在杰斐逊实验室的 A 厅进行，使用 11 GeV 纵向极化电子入射到 1.5 m 液态氢目标上。环形光谱仪将用于将莫勒电子与氢中质子散射的电子分开，并将它们聚焦在目标下游 28 m 的探测器平面上。散射电子的综合产量将通过 224 个石英切伦科夫探测器阵列进行测量。******MOLLER 实验将与在对撞机上进行的弱混合角的两个最精确测量中的任何一个一样好，并且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。由于其精度，MOLLER 具有超越标准模型的物理发现潜力，其接触相互作用尺度远远超过 10 TeV，这一灵敏度水平在未来十年内即使在对撞机上也无法达到。