Searches for Exotic Spin-Dependent Forces using High-Frequency Mechanical Oscillators

使用高频机械振荡器搜索奇异的自旋相关力

• 批准号: 1707986
• 负责人: Joshua Long
• 金额: $ 24万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1707986&HistoricalAwards=false
• 关键词: Searches; Exotic; Spin; Dependent; Forces

This award supports an experimental search for fundamental forces of nature beyond gravity and electromagnetism at sub-millimeter length scales. Forces could depend on several properties of the test objects involved, such as mass (like gravity), or charge (like electromagnetism). The proposed experiments concentrate on forces that depend on spin, which can be thought of as the rotation of an object around its axis. Most subatomic particles (including the protons, neutrons, and electrons of ordinary matter) have non-zero spin, which determines their magnetic properties: magnetic forces depend on spin. The discovery of an additional macroscopic force that depends on spin would have enormous implications for physics from subatomic to cosmological scales. A variety of extensions to the Standard Model (the most successful theory of particle physics to date, but widely believed to be incomplete) predict short-range spin-dependent forces. These forces are mediated by particles that could contribute to "dark matter," the otherwise unknown quantity hypothesized to make up about one quarter of the mass of the universe and to explain the apparent mass distributions of galaxies. During its execution, this fundamental project will also provide all participants (including undergraduates who have contributed to this proposal) with experience in mechanical design, vacuum technology, low-noise electronics, semiconductor and magnetic materials processing, and other practical techniques useful in a wide range of science and engineering fields. The experiment will also be a key focus of the Indiana University Center for Spacetime Symmetries (IUCSS), which was founded by the PI and his colleagues to strengthen and publicize IU's growing expertise in the investigation of the structure of spacetime.The experiment uses 1-kilohertz planar oscillators as test masses with a thin shield between them to suppress backgrounds, a technique that has demonstrated the capability to probe micron-scale distances using relatively large (square-centimeter) masses, and to operate at the limit of instrumental thermal noise at room temperature. The principal challenge will be to overcome the anticipated magnetic backgrounds associated with the use of polarized test masses. To this end we have developed spin-polarized test masses with very low intrinsic magnetism. We will use them in our experiments to conduct initial searches for several velocity-independent spin-coupled forces with unprecedented sensitivity below one millimeter, and to search for several more velocity-dependent interactions that are presently unconstrained by experiment. We will also investigate polarized materials that have the potential to improve our experimental sensitivity by several additional orders of magnitude. At the completion of the award period, it is our expectation that, in the absence of a discovery, we will have set limits on as many as eleven previously unconstrained spin-coupled interactions of electrons in the sub-millimeter range, and up to four more limits with sensitivity at least order of magnitude greater than present constraints.

该奖项支持在亚毫米长度尺度上对重力和电磁力以外的自然基本力进行实验研究。力可能取决于所涉及的测试对象的几种特性，例如质量（如重力）或电荷（如电磁）。提出的实验集中在依赖于自旋的力上，自旋可以被认为是物体绕其轴的旋转。大多数亚原子粒子（包括质子、中子和普通物质的电子）具有非零自旋，这决定了它们的磁性：磁力取决于自旋。发现一种依赖自旋的额外宏观力，将对从亚原子到宇宙尺度的物理学产生巨大影响。标准模型（迄今为止最成功的粒子物理学理论，但普遍认为是不完整的）的各种扩展预测了短程自旋依赖力。这些力是由可能构成“暗物质”的粒子介导的。暗物质是一种未知的物质，据推测，它约占宇宙质量的四分之一，并解释了星系的表观质量分布。在实施过程中，该基础项目还将为所有参与者（包括参与该提案的本科生）提供机械设计，真空技术，低噪声电子，半导体和磁性材料加工以及其他在广泛的科学和工程领域有用的实用技术方面的经验。该实验也将成为印第安纳大学时空对称中心（IUCSS）的重点，该中心是由PI和他的同事们建立的，旨在加强和宣传印第安纳大学在时空结构研究方面日益增长的专业知识。该实验使用1千赫兹平面振荡器作为测试质量，它们之间有一个薄屏蔽层来抑制背景，这种技术已经证明了使用相对较大（平方厘米）的质量探测微米级距离的能力，并且可以在室温下仪器热噪声的极限下工作。主要的挑战将是克服与使用极化测试质量有关的预期磁背景。为此，我们研制了具有极低本征磁性的自旋极化测试质量。我们将在实验中使用它们，以前所未有的灵敏度在一毫米以下，对几种与速度无关的自旋耦合力进行初步搜索，并寻找目前不受实验约束的几种与速度相关的相互作用。我们还将研究有可能将我们的实验灵敏度提高几个额外数量级的极化材料。在奖励期结束时，我们期望，在没有发现的情况下，我们将在亚毫米范围内设置多达11个以前不受约束的自旋耦合电子相互作用的限制，以及多达4个灵敏度至少比现有限制高数量级的限制。

项目成果

Combined Search for a Lorentz-Violating Force in Short-Range Gravity Varying as the Inverse Sixth Power of Distance

短程重力中洛伦兹破坏力的联合搜索随距离的六次方倒数变化

• DOI: 10.1103/physrevlett.122.011102
• 发表时间: 2019
• 期刊: Physical Review Letters
• 影响因子: 8.6
• 作者: Shao Cheng Gang;Chen Ya Fen;Tan Yu Jie;Yang Shan Qing;Luo Jun;Tobar Michael Edmund;Long J C;Weisman E;Kostelecky V Alan
• 通讯作者: Kostelecky V Alan