Search for Gravity-Like Forces at Sub-100 microns Scale

该奖项支持一项实验项目，该项目旨在探测超出基本粒子相互作用标准模型的物理理论所预测的距离为25微米的牛顿引力偏差。一个低温探测器已经建成，用来测量这些距离下的微小力。力传感器是一个微机械硅悬臂。一个金色的测试块被粘在悬臂的末端。金条和硅条的交替模式在测试质量以下振荡；测试质量与运动驱动质量的变化引力场之间的耦合激发了悬臂梁的共振。用光纤干涉仪测量悬臂梁的运动，并由此推导出质量之间的力。由于驱动质量的几何特性，随着驱动质量纵向平衡位置的变化，任何引力都会表现出明显的周期性。将测量到的力与有限元分析预测的力进行比较，得出了新的类引力的界限，这可能标志着新的物理学。虽然标准模型成功地统一了电磁、强相互作用和弱相互作用，但它忽略了引力。这给基础物理学带来了一个巨大的谜团：为什么即使是最微弱的亚原子力，即弱力，也比引力强得多？试图回答这个问题的现代理论预测，牛顿定律将在更长的尺度上修正，达到1毫米。本实验中使用的技术是微型制造设备的前沿技术。

This award supports an experimental program to probe deviations from Newtonian gravity at distances on the order of 25 microns as predicted by theories of physics beyond the Standard Model of fundamental particle interactions. A low temperature probe has been built to measure tiny forces expected at these distances. The force sensor is a micromachined silicon cantilever. A gold test mass is glued to the end of the cantilever. An alternating pattern of gold and silicon bars is oscillated below the test mass; the coupling between the test mass and the varying gravitational field of the moving drive mass excites the cantilever on resonance. A fiber interferometer measures the cantilever motion and from this measurement, the force between the masses is deduced. Due to the geometry of the drive mass, as the longitudinal equilibrium position of the drive mass is varied, any gravitational force will show a distinct periodicity. Comparison of the measured force to predictions from finite element analysis yields bounds on new gravity-like forces which could signal new physics.While the Standard Model successfully unifies the electromagnetic, the strong and the weak interactions, it ignores gravity. This poses a great mystery in fundamental physics: why is even this most feeble subatomic force, i.e. the weak force, so much stronger than gravity? Modern theories that attempt to answer this question predict modifications to Newton's law at much longer length scales, up to 1 millimeter. The technology used in this experiment is at the cutting edge of micro-fabricated devices.