Optimising ultra-light dark matter searches with ground-based interferometers

Ultra-light dark matter fields induce nearly monochromatic signals in gravitational-wave detectors through their coupling to the Standard Model. Their spectral morphology exhibits features caused by sidereal modulation that, for frequencies below $\sim 30$Hz, enable discrimination between spin-1 and spin-2 ultra-light dark matter signals, provided sufficient signal-to-noise ratio. In the context of LIGO–Virgo–KAGRA search techniques, we show that incorporating these spectral features can improve current excess-power constraints at low frequencies by up to $\sim 36\mathrm{\%}$. Additionally, we propose an optimised implementation of the cross-correlation statistics within the Band-Sampled-Data framework, enhancing the sensitivity of cross-correlation searches across nearly the entire frequency range, reaching up to $\sim 42\mathrm{\%}$ at low frequencies and $\sim 35\mathrm{\%}$ at high frequencies.