Probing Light Particles With Optically Trapped Sensors Through Nucleon Scattering

Optically levitated nanospheres are highly sensitive to the motion of their center of mass even under small momentum transfer. We propose detecting exotic particles via nucleon scattering in such spheres in the context of an ongoing experiment. The 200 nm-diameter spheres within the present experimental realization, featuring a configuration of the array $4\times 4$ and its upgrade, can achieve sensitivity to nuclear couplings of ALPs exclusively and pseudoscalar dark matter in the $\sim 10$ keV mass range, targeting previously unconstrained regions of parameter space. In contrast, a smaller sphere with a diameter of 15 nm benefits from overall coherence enhancement, enabling the detection of pseudoscalar and vector dark matter down to $\mathcal{O}(100)$ eV even with a single sphere. This smaller setup also offers the potential for the direct detection of Earth-bound dark matter strongly coupled with visible matter, even with its minimal velocity and tiny fractional abundance.