Vector dark matter at the LHC
  We consider monojet searches at the Large Hadron Collider (LHC) for spin-1
dark matter that interacts with quarks through a contact operator. If the dark
matter particles are produced with longitudinal polarizations, then the
production matrix element is enhanced by factors of the energy. We show that
this particularly effective search strategy can test models for which the
energy suppression scale of the operator is as large as 10^5 TeV. As such,
these searches can probe a large class of models for which the contact-operator
approximation is valid. We find that for contact operators that permit
velocity-independent dark matter-nucleon scattering, LHC monojet searches for
spin-1 dark matter are competitive with or far surpass direct-detection
searches depending on whether the scattering is spin independent or spin
dependent, respectively.
