High-Frequency Search for New Sub-Millimeter Range Forces

高频搜索新的亚毫米范围力

• 批准号: 1207656
• 负责人: Joshua Long
• 金额: $ 22.3万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1207656&HistoricalAwards=false
• 关键词: Frequency; Search; New; Sub; Millimeter

This award supports an experimental search for spin-dependent forces below 1 millimeter. Present experimental limits allow for undiscovered forces in nature several million times stronger than gravity acting over distances resolvable by the unaided eye. Theoretical models developed over the past few decades that attempt to explain why interactions involving the strong nuclear force always conserve certain spacetime symmetries make specific predictions of spin-dependent forces in the sub-millimeter range. The proposed experiment thus represents an excellent opportunity for discoveries in this range. 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. Spin-polarized materials with high spin density but low intrinsic magnetism, including ferrimagnets that exhibit orbital compensation of the magnetism associated with the aligned electron spins, will be investigated as test masses. With modest aligned-spin densities but good control of magnetic backgrounds, the projected sensitivity of the experiment is several orders of magnitude greater than the current best limits at ranges below 1 millimeter.Spin is a fundamental property of elementary particles and a crucial aspect of quantum physics. The discovery of a 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 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 the "dark matter" hypothesized to pervade all of space in order to explain the apparent mass distributions of galaxies. The mysterious "dark energy" postulated to explain the observed expansion of the universe also seems to point to a length scale on the order of tens of microns as a special range at which previously undetected phenomena might appear. During its execution, this fundamental project will also provide all participants (including several 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. Success of the proposed experiment will support the IUCSS goal to establish a long-term program of coordinated experimental and theoretical investigation of new physics at sub-millimeter length scales.

该奖项支持对1毫米以下自旋相关力的实验研究。目前的实验限制允许在自然界中存在比重力强几百万倍的未被发现的力，这些力作用在肉眼可以分辨的距离上。过去几十年来发展起来的理论模型试图解释为什么涉及强核力的相互作用总是保持一定的时空对称性，并对亚毫米范围内的自旋相关力做出了具体预测。因此，拟议的实验代表了在这个范围内发现的绝佳机会。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。具有高自旋密度但低本征磁性的自旋极化材料，包括表现出与排列的电子自旋相关的磁性的轨道补偿的铁磁体，将作为测试质量进行研究。由于对准自旋密度适中，但对磁背景控制良好，实验的预测灵敏度比目前在1毫米以下范围内的最佳极限高出几个数量级。自旋是基本粒子的基本性质，也是量子物理学的一个重要方面。发现一种依赖于自旋的宏观力将对从亚原子到宇宙尺度的物理学产生巨大的影响。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。这些力是由粒子介导的，这些粒子可能有助于“暗物质”的假设，这些暗物质遍布所有的空间，以解释星系的表观质量分布。用来解释观测到的宇宙膨胀的神秘的“暗能量”似乎也指向了一个几十微米量级的长度尺度，在这个特殊的范围内，以前未被发现的现象可能会出现。在实施过程中，该基础项目还将为所有参与者（包括为该提案做出贡献的几名本科生）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。该实验的成功将支持IUCSS建立亚毫米尺度新物理的协调实验和理论研究的长期计划的目标。