Experimental Limits on Planetary Mass Primordial Black Hole Mergers

The multimode acoustic gravitational wave experiment (MAGE) is a high-frequency gravitational wave detection experiment featuring cryogenic quartz bulk acoustic wave resonators operating as sensitive strain antennas in the MHz regime. After 61 days of noncontinuous data collection, we present bounds on the observable merger rate density of primordial black hole binary systems of chirp mass 1.2×10^{-4}M_{⊙}<M<1.7×10^{-9}M_{⊙}. The maximum achieved limit on the merger rate density is R<1.3×10^{18} kpc^{-3} yr^{-1}, which corresponds to constraining yearly mergers to a distance of reach on the order of the Solar System, or 1.0×10^{-6} kpc during the observational period. In addition, we exclude significantly rare and strong events similar to those observed in previous predecessor experiments as nongravitational background signals, utilising coincident analysis between multiple detectors.