Lepton Magnetic Moments and Fine Structure Constant

轻子磁矩和精细结构常数

• 批准号: 1903756
• 负责人: Gerald Gabrielse
• 金额: $ 81.95万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1903756&HistoricalAwards=false
• 关键词: Lepton; Magnetic; Moments; Fine; Structure

The most precise prediction made to date by a fundamental physical theory is that of a "magnetic moment," the strength of the magnet within the fundamental particle of electricity (the electron) and its antimatter counterpart (the positron). So far, measurements of the magnetism of these particles agree with prediction to a very high precision--much more precisely than those who formulated the theory ever expected. This is despite the fact that the same theory has serious problems: it predicts that no universe would survive after a big bang, and it has not been able to explain why the universe is made of matter rather than antimatter. What is wrong in our mathematical description, and the source of the fundamental imbalance between the properties of matter and antimatter, have yet to be discovered. This project will investigate such problems by measuring an electron's or positron's magnetism even more precisely than before. To do so, a single elementary particle will be suspended for months at a time. Batteries and magnets will keep the charged particle from colliding with any apparatus. Cooling the apparatus to nearly absolute zero will make a nearly perfect vacuum. To measure the magnetism, the separations of the lowest energy levels of the system will be probed by stimulating transitions between these levels using radio waves, and measuring the frequency of the waves that make these transitions occur most rapidly. This project promises to improve the measurement precision by an order of magnitude or more by stimulating two transitions simultaneously. Methods developed as part this project so far are being used to stabilize the magnets in magnetic resonance imaging (MRI) and to analyze the constituents of modern pharmaceuticals via ion cyclotron resonance (ICR) analysis. In more technical detail, a single electron or positron will be suspended in the electric and magnetic fields of a cylindrical Penning trap. Refrigeration below 0.1 kelvin will allow cryopumping to produce a nearly perfect vacuum and eliminate blackbody photons from the cylindrical cavity formed by the metal trap electrodes so the electron can radiate down to a cyclotron ground state. Electromagnetic driving forces will stimulate further cooling of the particle, and others will stimulate changes in its cyclotron and spin state. These one-quantum changes will be detected using quantum non-demolition methods that keep repeated detections from changing the quantum states of interest. Spontaneous emission of the particle's cyclotron motion will be inhibited, using a combination of the choice of the magnetic field strength and the cavity size, to give averaging times long enough for detecting a single quantum state of a single particle. The magnetic moment in natural units is essentially the measured ratio of the particle's spin and cyclotron frequencies, both of which will be measured simultaneously to greatly reduce the effect of tiny but unavoidable drifts of the magnetic field. The measured magnetic moments, the most precisely measured properties any elementary particle, will test of the most precise prediction of the standard model of particle physics at an unprecedented precision.

迄今为止，通过基本物理理论做出的最精确的预测是“磁矩”，即电力（电子）及其反物质对应物（Potitron）内磁体的强度。到目前为止，这些颗粒的磁性测量值与预测非常高的预测相比，比制定了有史以来预期的理论的人更精确。尽管相同的理论有严重的问题：它预测，大爆炸后没有宇宙能够生存，并且无法解释为什么宇宙是由物质而不是反物质制成的。我们的数学描述中有什么问题，以及物质和反物质属性之间的根本不平衡的根源。该项目将通过比以前更精确地测量电子或正电子的磁性来调查此类问题。为此，一次单一的基本粒子一次悬浮几个月。电池和磁铁将使带电粒子与任何设备相撞。将设备冷却至绝对零将产生几乎完美的真空。为了测量磁性，将通过使用无线电波刺激这些水平之间的过渡，并测量使这些过渡的波的频率进行探测，从而探测系统的最低能级的分离。该项目有望通过同时刺激两个过渡来提高测量精度。到目前为止，该项目开发为部分项目，用于稳定磁共振成像（MRI）中的磁铁，并通过离子回旋共振（ICR）分析分析现代药物的组成部分。从更具技术性的详细信息中，单个电子或正电子将悬挂在圆柱笔陷阱的电和磁场中。 低于0.1开尔文的制冷将允许冷冻倾斜产生几乎完美的真空，并消除由金属陷阱电极形成的圆柱腔中的黑体光子，因此电子可以辐射到旋风基团态。 电磁驱动力将刺激粒子的进一步冷却，而其他驱动力将刺激其回旋体和自旋状态的变化。 这些单量子的变化将使用量子非解析方法检测到，以防止重复检测改变感兴趣的量子状态。 使用磁场强度和空腔大小的选择的组合，将抑制粒子回旋体运动的自发发射，以给出足够长的时间来检测单个粒子的单个量子状态。 天然单元中的磁矩本质上是粒子自旋和回旋频率的测量比，这两个将同时进行测量，以大大降低磁场的微小但不可避免的漂移的效果。 测得的磁矩，最精确测量的任何基本粒子，将以前所未有的精度测试粒子物理标准模型的最精确预测。