  We study current constraints and search prospects for a GeV scale vector
boson at a range of low energy experiments. It couples to the Standard Model
charged particles with a strength <= 10^-3 to 10^-4 of that of the photon. The
possibility of such a particle mediating dark matter self-interactions has
received much attention recently. We consider searches at low energy high
luminosity colliders, meson decays, and fixed target experiments. Based on
available data, searches both at colliders and in meson decays can discover or
exclude such a scenario if the coupling strength is on the larger side. We
emphasize that a dedicated fixed target experiment has a much better potential
in searching for such a gauge boson, and outline the desired properties of such
an experiment. Two different optimal designs should be implemented to cover the
range of coupling strength 10^-3 to 10^-5, and < 10^-5 of the photon,
respectively. We also briefly comment on other possible ways of searching for
such a gauge boson.
