  Typical searches for supersymmetry cannot test models in which the two
lightest particles have a small ("compressed") mass splitting, due to the small
momentum of the particles produced in the decay of the second-to-lightest
particle. However, datasets with large missing transverse momentum ($E_{\rm
T}^{\rm miss}$) can generically search for invisible particle production and
therefore provide constraints on such models. We apply data from the ATLAS
mono-jet (jet+$E_{\rm T}^{\rm miss}$) and vector-boson-fusion (forward jets and
$E_{\rm T}^{\rm miss}$) searches to such models. The two datasets have
complementary sensitivity, but in all cases experimental limits are at least
five times weaker than theoretical predictions.
