binning used in DØ analysis. The data was collected between 2002 − 2005 using jet triggers with four thresholds: 20, 50, 70 and 100 GeV /c . In order to not saturate the data acquisition system by jet triggers, only 1/808, 1/35, 1/8 of lower threshold triggers were recorded. The transverse energy of each jet is corrected on average to form the jet p$_{T}$ spectrum which was corrected for bin-to-bin migration of jets due to finite jet energy resolution. CDF used simulated events to evaluate the smearing corrections. The corrections depend on the shape of the true jet p$_{T}$ spectrum and the jet energy resolution. A large sample of QCD jet events was generated using the pythia event generator [8] and passed through the CDF detector simulation. The detector simulation was tuned to describe the single particle response measured in p ¯ p collisions [37]. These simulated data were analyzed using the same procedure as the one used for the real data to obtained the smeared spectrum. The bin-to-bin migration effect was determined by taking the ratio of smeared jet spectrum and the particle jet spectrum. For this procedure to be valid, the smeared p$_{T}$ spectrum of the simulated events must match the spectrum measured in data. The two spectra are very close but not exactly same. The simulated particle jet smeared p$_{T}$ spectrum was adjusted (re-weighted) to force it to agree with the measured spectrum. Re-weighting changes the unsmearing corrections by only a few percent. The unsmearing correction is < 5% for p jet T < 300 GeV /c and increases to as much as 20% at p$_{T}$ = 500 GeV /c . The corrected jet p$_{T}$ spectrum is compared to perturbative QCD predictions evaluated with the FastNLO [17] program using the CTEQ6.1M parton distribution functions [50]. The renormalization and factorization scales ( µ$_{R}$, µ$_{F}$ ) are chosen to be p$_{T}$ /2, which are the same as used in the global QCD analysis to determine the PDFs [50]. Using µ$_{R}$ = µ$_{F}$ = p jet T gives up to 10% smaller predictions in the cross section. The perturbative QCD predictions are corrected for underlying event and hadronization effects measured using the procedure described in Section II. While clustering the partons produced by the FastNLO, CDF used an ad-hoc parameter R$_{sep}$ which was introduced to mimic the split and merge procedure in iterative cone clustering algorithms [51]. At order α 3 $_{s}$, the final state can have up to three partons. Depending on their relative p$_{T}$ and their separation in y − φ space, these partons are clustered into two or three jets, Two partons are clustered into a single jet if they are within R from the jet centroid and within R × R$_{sep}$ of each other. A value of R$_{sep}$ = 1 . 3 is used in this calculation. An R$_{sep}$ = 2 . 0 (i.e. the midpoint algorithm without R$_{sep}$ ) yields less than a 5% increase in cross section for NLO QCD predictions. As shown in Figure 4, the 20