two heavy particles, each decaying to an unseen particle plus jets. Such processes include SUSY particle production with various decay chains, the simplest example of which is the pair production of squarks, where each squark decays to a quark and the LSP, with the LSP assumed to be stable and weakly interacting. In processes with two or more undetected energetic final-state particles, it is not possible to fully reconstruct the event kinematics. Event-by-event, one cannot make precise assignments of the reconstructed final-state particles (leptons, jets, and undetected neutrinos and LSPs) to each of the original superpartners produced. For a given event, there is not enough information to determine the mass of the parent particles, the subprocess center-of-mass energy $\sqrt{\hat{s}}$, the center-of-mass frame of the colliding protons, or the rest frame of the decay of either parent particle. As a result, it is challenging to distinguish between SUSY signal events and SM background events with energetic neutrinos, even though the latter involve different topologies and mass scales. It is also challenging to identify events with instrumental sources of that can mimic the signal topology.

The razor approach [@razor2010; @rogan] addresses these challenges through a novel treatment of the event kinematics. The 