  We study the sensitivity to sub-GeV dark sectors of high energy ($ \geq100$
GeV) proton fixed target experiments such as the Main Injector and the future
Long-Baseline Neutrino Facility (LBNF). We focus on off-axis detectors since
they have been shown to be the ideal location to reduce the neutrino
background. We consider MiniBooNE as an off-axis detector for the NuMI facility
and a hypotetical detector for LBNF located 200 m away from the target and 6.5
degrees off-axis. We find that with the existing data, MiniBoone can explore
new regions of the parameter space for leptophobic dark forces in the 100 MeV-
few GeV mass range. The dedicated MiniBooNE run in beam dump mode would further
improve the reach for even lighter masses. Therefore, MiniBooNE has the
potential to be one of the most sensitive probe of leptophobic dark forces for
masses between 1 MeV-10 GeV.
