  We report the first results of a search for leptophobic dark matter (DM) from
the Coherent CAPTAIN-Mills (CCM) liquid argon (LAr) detector. An engineering
run with 120 photomultiplier tubes (PMTs) and $17.9 \times 10^{20}$
protons-on-target (POT) was performed in Fall 2019 to study the characteristics
of the CCM detector. The operation of this 10-ton detector was strictly
light-based with a threshold of 50 keV and used coherent elastic scattering off
argon nuclei to detect DM. Despite only 1.5 months of accumulated luminosity,
contaminated LAr, and non-optimized shielding, CCM's first engineering run
already achieved sensitivity to previously unexplored parameter space of light
dark matter (LDM) models with a baryonic vector portal. With an expected
background of 115,005 events, we observe 115,005+16.5 events which is
compatible with background expectations. For a benchmark mediator-to-dark
matter mass ratio of $m_{_{V_B}}/m_{\chi}=2.1$, DM masses within the range
$9\,\text{MeV} \lesssim m_\chi \lesssim 50\,\text{MeV}$ have been excluded at
90% C.L. in the leptophobic model after applying the Feldman-Cousins test
statistic. CCM's upgraded run with 200 PMTs, filtered LAr, improved shielding,
and ten times more POT will be able to exclude the remaining thermal relic
density parameter space of this model, as well as probe new parameter space of
other leptophobic DM models.
