role in constraining the gluon distribution at large x . The gluon distribution at low x are mainly determined from the scaling violations in lepton-nucleon scattering data. Normally, the results of these global analysis are fit at some initial scale µ$_{0}$ using tens of parameters. The PDF can be evolved to any arbitrary scale µ using QCD evolution equations which are available at NNLO approximation in perturbation theory. Both the MSTW [55] and CTEQ [56] collaborations have included Run II jet data in their global analysis to update the PDFs. The three Run II inclusive jet measurements are more accurate than Run I measurements, span a larger p$_{T}$ range and are consistent with each other [55]. As two CDF measurements used the same data, the MSTW collaboration decided to use the k$_{T}$ jet spectrum whereas the CTEQ collaboration is using the cone-based measurements. The Run I jet measurements do not play a significant role in the fit and thus the MSTW collaboration has dropped those data from the new fits. Comparisons of the gluon distribution g ( x ) determined in the new MSTW fit with the gluon distributions from MRST2004 [57] and CTEQ6.6 [58] fits along with the 90% uncertainty band are shown in Figure 6 (left) for µ 2 = Q 2 = 10 4 GeV $^{2}$. The new g ( x ) is lower than previous fits for x ≥ 0 . 3 but within the still large systematic uncertainties. As α$_{s}$ and g ( x ) always appear as a product, the values of α$_{s}$ and g ( x ) are strongly correlated. The value of α$_{s}$ in the three sets of PDFs is different and thus g ( x ) is also expected to be slightly different. The fractional uncertainty on the gluon distribution is shown in Figure 6 (right). At x = 0 . 4 and µ 2 = 10 4 GeV $^{2}$, the uncertainty reduces from 18% when the jet data are excluded from the fit to 12% when jet data are included in the fit. This modest extra constraint will make the predictions more precise at the LHC in processes where gluon-quark scattering dominates. $^{The hard cross section for jet production (}$̂ σ$_{ij}$ ) in Equation (1) at large p$_{T}$ can be expanded in powers of the strong coupling constant to the n th order in perturbation theory where the perturbative coefficients c ( m ) ij are functions of the kinematic variables and the factorization and renormalization scales only. The coefficients c ( m ) ij are available for m = 0 and m = 1. Using the jet cross section measurement, the strong coupling constant α$_{s}$ can D. Determination of the strong coupling constant ̂ σ$_{ij}$ = α 2 s n ∑ m =0 c ( m ) ij α m s . (7) 24