Collaborative Research: PM: RUI - Searches for Ultralight Bosonic Dark Matter with Atomic Magnetometer Networks

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Astrophysical observations indicate that up to 85% of the matter in the universe is unlike the matter that makes up our everyday world. What is this so-called dark matter? The answer to that question remains a mystery. One possibility is that dark matter could be in the form of large-scale structures (many times the size of the Earth) that couple weakly to ordinary matter. Another possibility is that the dark matter could be in the form of waves of varying intensity. If such structures or waves were to pass through the Earth they might interact with atoms and cause effects similar to those from a magnetic field. This grant will provide support for three undergraduate institutions, California State University – East Bay, Oberlin College, and Bucknell University, to work with an international team to search for dark matter of this kind. The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a collaboration of fifteen institutions throughout the world that have constructed precision atomic magnetometers that are capable of detecting such signals from dark matter. The data from the magnetometer network are analyzed to look for correlations that would indicate the Earth’s passage through dark matter structures or waves. The principal investigators will work with undergraduate students to develop more sensitive detectors for the network, analyze the network data, and work with the worldwide collaboration to detect dark matter. These measurements will give insight into the possible forms of dark matter and lead to a better understanding of the makeup of our universe while providing crucial research experience and training for the next generation of scientists. A well-motivated candidate for dark matter consists of ultralight bosons such as axions, axion-like particles (ALPs), or hidden photons with very low mass (much less than 1 eV). Ultralight bosonic fields can form stable, macroscopic configurations such as topological defects or boson stars due to, for example, self-interactions. Even in the absence of such effects, bosonic dark matter fields exhibit stochastic fluctuations. Additionally, it is possible that cataclysmic astrophysical events could produce intense bursts of exotic ultralight bosonic fields. In any of these scenarios, instead of being bathed in a uniform flux, terrestrial detectors will witness transient events when ultralight bosonic fields pass through Earth. The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of more than a dozen time-synchronized optical atomic magnetometers searching for correlated signals that is sensitive to transient signals due to spin-dependent interactions with ultralight bosonic fields. GNOME magnetometers have multi-layer magnetic shields that reduce external magnetic noise but allow most types of bosonic dark matter to penetrate within with no loss of sensitivity. A prominent exception is hidden photons, whose signals can be significantly reduced by shielding. To search for hidden photon dark matter, the principal investigators and undergraduate researchers will construct a new network of unshielded magnetometers, based on the GNOME architecture, located in magnetically quiet environments. The proposed experiments will probe a wide range of unexplored parameter space describing ultralight bosonic fields.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.