RUI: Search for Anomalous Spin Interactions with Atomic Comagnetometers

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Our research program encompasses two different projects. The first project is an experimental search for a long-range interaction between atomic spins and the mass of the Earth. Such an interaction could arise due to a heretofore undiscovered "fifth force" or if gravity, as opposed to being a purely tensor interaction as assumed in general relativity, has a scalar/pseudoscalar component. Recent theoretical work has shown that such interactions could be the cause of the accelerating expansion of the universe, commonly attributed to dark energy. Our experiment seeks to detect this effect by simultaneously measuring the spin precession of two isotopes of rubidium using laser spectroscopy. Our experiment aims to improve experimental sensitivity to long-range spin-mass interactions by 1-3 orders of magnitude. Our second project focuses on development of a prototype sensor for the Global Network of Optical Magnetometers for Exotic physics (GNOME), an array of geographically separated, time-synchronized ultrasensitive atomic comagnetometers that will search for correlated transient signals heralding new physics. The GNOME would be sensitive to nuclear and electron spin couplings to various exotic particles and fields. To date, no such search has ever been carried out, making the GNOME a novel experimental window on new physics. A specific, feasible example of new physics detectable with the GNOME, presently unconstrained by astrophysical observations and laboratory experiments, is a network of domain walls of light pseudoscalar fields.Our present understanding of fundamental physics is confronted by a number of deep mysteries: the origin of the matter-antimatter asymmetry of the universe, the nature of dark energy, and the nature of dark matter. Our experiments, conducted in laboratories on Earth, use precise measurements of atomic spins to test several hypotheses that might explain these mysteries. It has been proposed that if our present theory of gravity is incomplete, additional components of gravity could both generate the dark energy pushing the universe apart and produce an excess of matter over antimatter after the Big Bang. These additional components of gravity would also cause atomic spins to precess in the Earth's gravitational field, the effect for which our experiment will search. A possible explanation of dark matter is a network of invisible galactic-scale "domain walls" that store considerable mass and energy. These invisible domain walls would exert a small torque on atomic spins that could be detected when the Earth passes through a wall. We are building a prototype sensor sensitive to such torques from domain wall-crossing events. An array of time-synchronized sensors based on our prototype will search for transient signals of astrophysical origin heralding such new physics. Our research is being carried out at a public undergraduate institution with a diverse student body, providing hands-on experience in state-of-the-art experimental physics to many undergraduate students (including a significant number of women and underrepresented minorities).