Missing energy look-alikes with100pb−1at the CERN LHC

A missing energy discovery is possible at the LHC with the first $100{\mathrm{pb}}^{-1}$ of understood data. We present a realistic strategy to rapidly narrow the list of candidate theories at, or close to, the moment of discovery. The strategy is based on robust ratios of inclusive counts of simple physics objects. We study specific cases showing discrimination of look-alike models in simulated data sets that are at least 10 to 100 times smaller than used in previous studies. We discriminate supersymmetry models from nonsupersymmetric look-alikes with only $100{\mathrm{pb}}^{-1}$ of simulated data, using combinations of observables that trace back to differences in spin.