  Collider signals of dark photons are an exciting probe for new gauge forces
and are characterized by events with boosted lepton jets. Existing techniques
are efficient in searching for muonic lepton jets but due to substantial
backgrounds have difficulty constraining lepton jets containing only electrons.
This is unfortunate since upcoming intensity frontier experiments are sensitive
to dark photon masses which only allow electron decays. Analyzing a recently
proposed model of kinetic mixing, with new scalar particles decaying into dark
photons, we find that existing techniques for electron jets can be
substantially improved. We show that using lepton-jet-substructure variables,
in association with a boosted decision tree, improves background rejection,
significantly increasing the LHC's reach for dark photons in this region of
parameter space.
