Speaker
Description
Single-photon atom gradiometry is a powerful experimental technique that can be employed to search for the oscillation of atomic transition energies induced by ultra-light scalar dark matter (ULDM). Previous studies have focused on the sensitivity reach of these experiments down to ULDM masses of order ~0.1 Hz, below which gravity gradient noise (GGN) is expected to dominate over atom shot noise (ASN). In this work, after presenting a likelihood-based analysis that simultaneously accounts for a DM signal in an underground GGN and ASN background, we quantify for ULDM searches the potential benefit of a vertical multi-gradiometer experiment, which consists of three or more coupled atom interferometers along the same baseline, thus showing how GGN underground can be mitigated if not entirely cancelled in specific gradiometer configurations. Hence, we provide more robust projections for the sensitivity of vertical gradiometers like AION to scalar ULDM down to e-3 Hz, where scalar DM parameter space is still unconstrained by other experiments.
