Can LIGO Detect Asymmetric Dark Matter?

Dark matter from the galactic halo can accumulate in neutron stars and transmute them into sub-2.5 $M_\odot$ black holes if the dark matter particles are heavy, stable, and have interactions with nucleons. We show that non-detection of gravitational waves from mergers of such low-mass black holes can constrain the interactions of asymmetric dark matter particles with nucleons. We find benchmark constraints with LIGO O3 data, viz., $\sigma_{\chi n} \geq {\cal O}(10^{-47})$ cm$^2$ for bosonic DM with $m_\chi\sim$ PeV (or $m_\chi\sim$ GeV, if they can Bose-condense) and $\geq {\cal O}(10^{-46})$ cm$^2$ for fermionic DM with $m_\chi \sim 10^3$ PeV. These bounds depend on the priors on DM parameters and on the currently uncertain binary neutron star merger rate density. However, if null-detection continues with increased exposure over the next decade, LIGO will set remarkable constraints. We find the forecasted sensitivity to heavy asymmetric dark matter to be world-leading, viz., dipping many orders of magnitude below the neutrino floor and completely testing the dark matter solution to missing pulsars in the Galactic center, and demonstrate a windfall science-case for gravitational wave detectors.