  Despite being mostly secluded, dark sector particles may feebly interact with
photons via a small mass-dimension 4 millicharge, a mass-dimension 5 magnetic
and electric dipole moment, or a mass-dimension 6 anapole moment and charge
radius. If sufficiently light, the LHC may produce an intense and collimated
beam of these particles in the far forward direction. We study the prospects of
searching for such dark sector particles with electromagnetic form factors via
their electron scattering signature in the Forward Liquid Argon Experiment
(FLArE) detector at the Forward Physics Facility (FPF). We find that FLArE can
provide new probes of sub-GeV dark particles with dipole moments and strong
sensitivities for millicharged particles in the 100 MeV to 100 GeV region. This
complements other search strategies using scintillation signatures or dark
matter direct detection and allows for probing strongly interacting dark matter
motivated by the EDGES anomaly. Along with the FORMOSA detector, this leads to
a very diverse and leading experimental program in the search for millicharged
particles in the FPF.
