  We investigate constraints on the dark photon arising from an analysis of
deep inelastic scattering (DIS) data. We perform extractions of parton
distribution functions (PDFs) with and without a dark photon being present and
allow the dark photon mixing parameter and mass to vary. We also include the
effects of vector meson dominance to ensure the correct photo-production limit.
By considering the variation of the total $\chi^2$ arising from such
extractions we infer exclusion limits on the kinetic mixing parameter of the
dark photon for dark photon mass up to $80\ {\rm GeV}$.
