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

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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.