  Beam dumps and fixed-target experiments have been very sensitive probes of
such particles and other physics beyond the Standard Model (BSM) by considering
the production of new states from the primary interaction in the beam dump. In
a proton beam dump, there are many secondary interactions taking place in
electromagnetic showers which may be additional production channels for
pseudoscalar bosons or axion-like particles (ALPs). The target-less
configuration of the MiniBooNE experiment, which collected data from $1.86
\times 10^{20}$ protons impinging directly on the steel beam dump, is an
excellent test of sensitivity to these production channels of ALPs in the MeV
mass region. Using the null observation of the MiniBooNE dump mode data, we set
new constraints on ALPs coupling to electrons and photons produced through a
multitude of channels and detected via both scattering and decays in the
MiniBooNE detector volume. We find that the null result rules out parameter
space that was previously unconstrained by laboratory probes in the 10-100 MeV
mass regime for both electron and photon couplings. Lastly, we make the case
for performing a dedicated analysis with 1.25$\times 10^{20}$ POT of data
collected by the ArgoNeuT experiment, which we show to have complementary
sensitivity and set the stage for future searches.
