Gravitational search for near-Earth primordial black holes or other compact dark objects*

Dark matter has been a mysterious entity, escaping detection and remaining hidden from all who seek it.  What is known is that it weakly interacts with gravity.  Here, we search for dark matter objects in the form of potential primordial black holes orbiting the earth using measurements of local gravitational acceleration.  There have been similar searches for dark matter orbiting within the inner core of the Earth.  Using about 10 years of data from the superconducting gravimeter located in the Black Forest Observatory (in Southwest Germany) and Djougou Station (in West Africa), we analyze and define an upper limit for the maximum mass for such PBHs orbiting Earth.  This was done by accounting for factors such as the composition and quadrupole moment of the Earth, the Earth's moon Luna, and noise and atmospheric effects on the gravimeter and running simulations for different types of orbits (variable inclination angles and eccentricities) for potential PBHs.  The excluded mass for any such Earth-orbiting PBHs was 1017g or larger for orbits of semimajor axes within two Earth radii.  As the lower and upper bound for the masses are constrained by Hawking radiation (<1017g) and microlensing (>1022g), in this study, we conclude that near-Earth PBHs are highly unlikely.