At the Large Hadron Collider (LHC), many new physics signatures feature pair-production of massive particles with subsequent direct or cascading decays to weakly interacting particles, such as SUSY scenarios with conserved R-parity or $H \to W(\ell\nu)W(\ell\nu)$, often motivated by models of new physics which attempt to mitigate the hierarchy problem in the Standard Model. While final states containing multiple weakly interacting particles represent an opportunity for discovery of new physics phenomena, they also present a unique experimental challenge; the kinematic information lost through particles escaping detection makes fully reconstructing these collision events impossible. In order to address this shortcoming special kinematic variables are used to partially reconstruct these events, providing sensitivity to properties of the particles appearing in them, including masses and even their spin correlations. We discuss a collection kinematic variables developed to study final states with weakly interacting particles at the LHC, focusing on the {\it super-razor} variables. Using the examples of searches for slepton and charging pair-production at the LHC, the motivation and derivation of these observables are described along with comparisons to previously existing approaches. Generalizations of the super-razor variables to more complicated decay topologies are also discussed, using fully leptonic top quark pair production as an example, along with its supersymmetric analogue of stop pair-production with subsequent decays to $b$-quarks and charginos.

This talk will cover our paper "Super-razor and searches for sleptons and charginos at the LHC" (Phys. Rev. D 89, 055020 http://journals.aps.org/prd/abstract/10.1103/PhysRevD.89.055020). In addition it will discuss generalizations of the proposed kinematic variables to more complicated final states (paper in preparation)