First dark matter search results from Coherent CAPTAIN-Mills

This paper describes the operation of Coherent CAPTAIN-Mills (CCM) detector located at Lujan Neutron Science Center (LANSCE) Los Alamos National Laboratory (LANL). CCM is a 10-ton liquid argon (LAr) 20 meters from high flux neutron/neutrino source and designed to search for sterile neutrinos ($\nu_s$) light dark matter (LDM). An engineering run was performed in Fall 2019 study characteristics CCM120 by searching coherent scattering signals consistent with $\nu_s$'s LDM resulting $\pi^+$ $\pi^0$ decays tungsten target. New parameter space leptophobic model excluded DM masses between $\sim2.0$ 30 MeV. The lessons learned this have guided development construction new CCM200 that will begin operations 2021 significantly improve on these searches.