  Dark matter pair production at high energy colliders may leave observable
signatures in the energy and momentum spectra of the objects recoiling against
the dark matter. We use LEP data on mono-photon events with large missing
energy to constrain the coupling of dark matter to electrons. Within a large
class of models, our limits are complementary to and competitive with limits on
dark matter annihilation and on WIMP-nucleon scattering from indirect and
direct searches. Our limits, however, do not suffer from systematic and
astrophysical uncertainties associated with direct and indirect limits. For
example, we are able to rule out light (< 10 GeV) thermal relic dark matter
with universal couplings exclusively to charged leptons. In addition, for dark
matter mass below about 80 GeV, LEP limits are stronger than Fermi constraints
on annihilation into charged leptons in dwarf spheroidal galaxies. Within its
kinematic reach, LEP also provides the strongest constraints on the
spin-dependent direct detection cross section in models with universal
couplings to both quarks and leptons. In such models the strongest limit is
also set on spin independent scattering for dark matter masses below ~4 GeV.
Throughout our discussion, we consider both low energy effective theories of
dark matter, as well as several motivated renormalizable scenarios involving
light mediators.
