key points of this approach are listed below.

-   The visible particles (leptons and jets) are used to define two *megajets*, each representing the visible part of a parent particle decay. The megajet reconstruction ignores details of the decay chains in favor of obtaining the best correspondence between a signal event candidate and the presumption of a pair-produced heavy particle that undergoes two-body decay.

-   Lorentz-boosted reference frames are defined in terms of the megajets. These frames approximate, event-by-event, the center-of-mass frame of the signal subprocess and the rest frames of the decays of the parent particles.The kinematic quantities in these frames can be used to extract the relevant SUSY mass scales.

-   The razor variables, ${\ensuremath{M_R}\xspace}$, ${\ensuremath{M_\mathrm{T}^R}\xspace}$, and ${\ensuremath{R}\xspace}\equiv {\ensuremath{M_\mathrm{T}^R}\xspace}/{\ensuremath{M_R}\xspace}$, are computed from the megajet four-momenta and the in the event. The ${\ensuremath{M_R}\xspace}$ variable is an estimate of an overall mass scale, which in the limit of massless decay products equals the mass of the heavy parent particle. It contains both longitudinal and transverse information, and its distribution peaks at the true value of the new-physics mass scale. The razor variable ${\ensuremath{M_\mathrm{T}^R}\xspace}$ is defined entirely from transverse information: the transverse momenta ($\pt$) of the megajets and the . This 