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

该奖项支持一项实验计划，以探测偏离牛顿引力的距离在25微米的数量级上，如基本粒子相互作用标准模型之外的物理理论所预测的那样。 一个低温探测器已经建成，以测量在这些距离预期的微小力量。力传感器是一个微机械硅悬臂梁。一个金色的测试块被粘在悬臂的末端。在测试质量块下方振荡交替图案的金和硅棒;测试质量块和移动驱动质量块的变化的重力场之间的耦合激励悬臂共振。光纤干涉仪测量悬臂梁的运动，并从该测量中推导出质量之间的力。由于驱动质块的几何形状，当驱动质块的纵向平衡位置变化时，任何重力将显示出明显的周期性。将测量到的力与有限元分析的预测进行比较，得出了新的类引力力的界限，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，也就是弱力，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在更长的长度尺度上的修正，可达1毫米。 本实验中使用的技术处于微制造设备的最前沿。

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.