Ratio of Isolated Photon Cross Sections in $\mathit{p}\overline{\mathit{p}}$ Collisions at $\surd \mathit{s}=630\mathrm{}$ and 1800 GeV

The inclusive cross section for production of isolated photons has been measured in $p\overline{p}$ collisions at $\sqrt{s}=630\mathrm{}\mathrm{GeV}$ with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy $\left(E_T\right)$ range from 7–49 GeV and have pseudorapidity $|\eta |<2.5\mathrm{}$. This measurement is combined with the previous D0 result at $\sqrt{s}=1800\mathrm{}\mathrm{GeV}$ to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the $E_T$ range.