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Jets produced by new physics are expected to be produced more centrally than by Standard Model processes and we expect a better signal to background ratio in the central region. Thus only those events in which two leading jets have | y | ≤ 1 . 0 are used. Moreover, the CDF calorimeter is best understood in this region. As shown in Figure 9, these data, after all corrections, are in good agreement with the NLO QCD calculations. The dijet mass spectrum before smearing corrections is shown in Figure 10. Smearing corrections are not used to avoid any degradation of the resonant structure, if any, in the data. The measured mass spectrum is fit to a smooth background given by 

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where p$_{0}$, p$_{1}$, p$_{2}$, and p$_{3}$ are free parameters. The dijet mass spectra predicted by pythia , herwig , and NLO pQCD can be described well by this functional form. The fit to the measured dijet mass spectrum is shown in Figure 10(a). The data are well described by this smooth function with a χ 2 of 16 for 17 degrees of freedom. The deviation from the smooth curve is shown in Figure 10(b). These data are used to determine the exclusion limits on the existence of new particles decaying into jets, as there is no evidence for the existence 

