  Monojet searches are a powerful way to place model-independent constraints on
effective operators coupling dark matter to the standard model. For operators
generated by the exchange of a scalar mediator, however, couplings to light
quarks are suppressed and the prospect of probing such interactions through the
inclusive monojet channel at the LHC is limited. We propose dedicated searches,
focusing on bottom and top quark final states, to constrain this class of
operators. We show that a search in mono b-jets can significantly improve
current limits. The mono-b signal arises partly from direct production of
b-quarks in association with dark matter, but the dominant component is from
top quark pair production in the kinematic regime where one top is boosted. A
search for tops plus missing energy can strengthen the bounds even more; in
this case signal and background have very different missing energy
distributions. We find an overall improvement by several orders of magnitude in
the bound on the direct detection cross section for scalar or pseudoscalar
couplings.
