Ratio of Jet Cross Sections ats=630GeV and 1800 GeV

The D0 Collaboration has measured the inclusive jet cross section in $\overline{p}p$ collisions at $\sqrt{s}=630\mathrm{}$ GeV. The results for pseudorapidities $||\left(\eta \right)<0.5\mathrm{}$ are combined with our previous results at $\sqrt{s}=1800\mathrm{}$ GeV to form a ratio of cross sections with smaller uncertainties than either individual measurement. Next-to-leading-order QCD predictions show excellent agreement with the measurement at 630 GeV; agreement is also satisfactory for the ratio. Specifically, despite a 10% to 15% difference in the absolute magnitude, the dependence of the ratio on jet transverse momentum is very similar for data and theory.