  A wealth of new physics models which are motivated by questions such as the
nature of dark matter, the origin of the neutrino masses and the baryon
asymmetry in the universe, predict the existence of hidden sectors featuring
new particles. Among the possibilities are heavy neutral leptons, vectors and
scalars, that feebly interact with the Standard Model (SM) sector and are
typically light and long lived. Such new states could be produced in
high-intensity facilities, the so-called beam dump experiments, either directly
in the hard interaction or as a decay product of heavier mesons. They could
then decay back to the SM or to hidden sector particles, giving rise to
peculiar decay or interaction signatures in a far-placed detector. Simulating
such kind of events presents a challenge, as not only short-distance new
physics (hard production, hadron decays, and interaction with the detector) and
usual SM phenomena need to be described but also the travel has to be accounted
for as determined by the geometry of the detector. In this work, we describe a
new plugin to the {\sc MadGraph5\_aMC@NLO} platform, which allows the complete
simulation of new physics processes relevant for beam dump experiments,
including the various mechanisms for the production of hidden particles, namely
their decays or scattering off SM particles, as well as their far detection,
keeping into account spatial correlations and the geometry of the experiment.
