4.  Events are assigned to final state “boxes” based on the presence or absence of a reconstructed lepton. This box partitioning scheme allows us to isolate individual SM background processes based on the final-state particle content and kinematic phase space; we are able to measure the yield and the distribution of events in the (${\ensuremath{M_R}\xspace}$, ${\ensuremath{R^2}\xspace}$) razor plane for different SM backgrounds. Events with at least one tagged $\cPqb$ jet are considered in a parallel analysis focusing on a search for the superpartners of third-generation quarks. In total, we consider 12 mutually exclusive final-state boxes: dielectron events (ELE-ELE), electron-muon events (ELE-MU), dimuon events (MU-MU), single-electron events (ELE), single-muon events (MU), and events with no identified electron or muon (HAD), each inclusive or with a $\cPqb$-tagged jet.

5.  For each box we use the low (${\ensuremath{M_R}\xspace}$, ${\ensuremath{R^2}\xspace}$) region of the razor plane, where negligible signal contributions are expected, to determine the shape and normalization of the various background components. An analytic model constructed from these results is used to predict the SM background over the entire razor plane.

6.  The data are compared with the prediction for the background in the sensitive regions of the razor plane and the results are 