Mass Measurement in Boosted Decay Chains with Missing Energy

We explore a novel method of mass reconstruction in events with missing transverse momentum at hadron colliders. In events with sizeable boost factors in the final steps of dual multi-stage decay chains, the missing energy particles may each be approximately collinear with a visible standard model particle, spanning a narrow "MET-cone." We exploit this collinear approximation, when applicable, to reconstruct the masses of exotica.