Dark Matter Search with Atomic Clocks Onboard GPS Satellites and Networks of Precision Measurement Devices

这个项目将有助于回答这个问题，“暗物质的本质是什么？”暗物质是看不见的，但已知它的存在。宇宙学观测表明，暗物质占宇宙中所有物质的85%，但其组成仍然是个谜。虽然暗物质的天文学证据是压倒性的，但到目前为止还没有人在实验室里探测到它，物理学家对它几乎一无所知。人们提出了许多暗物质组成的理论模型。确认或排除这些模型是很重要的，特别是如果这样做可以经济有效地完成。该项目将使用现有的全球定位系统（GPS）作为行星大小的暗物质探测器。这个小组将检查近二十年来GPS卫星上的原子钟的公开档案数据，并寻找暗物质团块对GPS原子钟记录的时间的短暂影响。由于GPS系统及其原子钟网络已经部署，这是一个相对低预算的项目，具有很高的潜在回报。如果这样的暗物质团块存在，并且这个项目发现了它们，这将对宇宙学和基本粒子物理学的基础产生影响。另一方面，如果暗物质团块不存在，那么能够断然排除这种可能性将是有价值的，有助于科学关注更可能的解释。不管怎样，这样的研究促进了科学的进步。这项研究还将有助于改进GPS数据的分析，这可以为许多其他应用提供好处，例如大地测量学，这对社会也有价值。雄心勃勃的计划一直在寻找重粒子形式的暗物质（DM），但没有确凿的证据，然而DM也可能来自形成宏观物体的超轻量子场。据预测，这样的物体会引起基本常数的明显变化，导致原子能级的瞬态变化。在目前的项目中，GPS。DM项目团队利用GPS卫星上的原子钟轨道网络作为5万公里口径的探测器来搜索这类DM物体。当地球穿过银河系DM光晕时，与DM的相互作用可能导致一系列原子钟扰动，这些扰动以银河系的速度在卫星星座中传播。挖掘16年的档案数据，当前项目的GPS。在当前的灵敏度水平上，DM没有发现以畴壁形式存在DM的证据，从而将某些二次标量耦合的限制提高了几个数量级。这个项目将把搜索扩展到几个不同类别的扩展DM对象，并极大地改进数据挖掘技术。这些技术有望将GPS暗物质探测器在DM候选质量参数空间的发现范围扩大4个数量级，在灵敏度上扩大2个数量级。本项目由粒子天体物理实验项目和原子、分子与光学物理实验项目联合资助。这两个项目都隶属于美国国家科学基金会数学与物理科学理事会物理系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will help answer the question, "What is the nature of dark matter?" Dark matter is invisible, yet it is known to exist. Cosmological observations indicate that dark matter makes up 85% of all matter in the Universe yet its composition remains a mystery. Although the astronomical evidence of dark matter is overwhelming, so far nobody has detected it in the laboratory, and physicists know almost nothing about it. Many theoretical models for dark matter composition have been put forward. It is important to either confirm or rule out such models, particularly if this can be done cost-effectively. This project will use the existing Global Positioning System (GPS) as a planet-sized dark matter detector. This team will examine nearly two decades of publicly available archival data from atomic clocks onboard GPS satellites and search for transient effects of dark matter clumps on time kept by the GPS atomic clocks. Since the GPS system and its network of atomic clocks is already deployed, this is a relatively low-budget project with high potential payoff. If such dark matter clumps exist and this project finds them, this would have an impact on the very foundations of cosmology and elementary particle physics. On the other hand, if dark matter clumps do not exist, it would be valuable to be able to rule this out categorically, to help science focus on more likely explanations. Either way, such investigations promote the progress of science. This research will also contribute to improvements in the analysis of GPS data, and this can provide a benefit for many other applications such as geodesy that are also of value to society. Ambitious programs have been searching for dark matter (DM) in the form of heavy particles with no conclusive evidence, yet DM could also arise from ultralight quantum fields that form macroscopic objects. Such objects are predicted to cause apparent variations of fundamental constants, leading to transient shifts in atomic energy levels. In its current project, the GPS.DM project team uses the orbiting network of atomic clocks on board GPS satellites as a 50,000-km-aperture detector to search for such DM objects. As the Earth moves through the galactic DM halo, interactions with DM could cause a sequence of atomic clock perturbations that propagate through the satellite constellation at galactic velocities. Mining 16 years of archival data, the current project of GPS.DM finds no evidence for DM in the form of domain walls at current sensitivity levels, thereby improving the limits on certain quadratic scalar couplings by several orders of magnitude. This project will expand the search to several different classes of extended DM objects and to dramatically improve data mining techniques. These techniques are anticipated to extend the discovery reach of the GPS dark matter detector by four orders of magnitude in the DM candidate mass parameter space and by two orders of magnitude in sensitivity.This project is jointly supported by the Particle Astrophysics Experiment program and the Atomic, Molecular and Optical Physics Experiment program. Both programs are in the Division of Physics in the NSF Directorate of Mathematical and Physical Sciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.