  If physics beyond the Standard Model contains metastable new particle states,
its signatures may manifest themselves at the LHC through the presence of
displaced vertices or displaced tracks. Such signatures are common in low-scale
supersymmetry breaking scenarios as well as a host of other well-studied new
physics models. Here we analyze the kinematics of dual cascade decays with
missing energy resulting from a stable non-interacting new particle state at
the bottom of the decay chain. We find that if the final step of the decay
chain involves a metastable particle, the resulting presence of displaced
tracks provides strong constraints with which to solve for the unknown
kinematic quantities lost through missing energy. In addition we develop
techniques with which to recover all kinematic unknowns, even in situations
where the unknown quantities outnumber the constraints. These techniques can
all be performed using a very small number of events and can thus be applied to
very early discovery level searches at the LHC.
