  Neutron production in antineutrino interactions can lead to bias in energy
reconstruction in neutrino oscillation experiments, but these interactions have
rarely been studied. MINERvA previously studied neutron production at an
average antineutrino energy of ~3 GeV in 2016 and found deficiencies in leading
models. In this paper, the MINERvA 6 GeV average antineutrino energy data set
is shown to have similar disagreements. A measurement of the cross section for
an antineutrino to produce two or more neutrons and have low visible energy is
presented as an experiment-independent way to explore neutron production
modeling. This cross section disagrees with several leading models'
predictions. Neutron modeling techniques from nuclear physics are used to
quantify neutron detection uncertainties on this result.
