Ratio of isolated photon cross sections in $p \bar{p}$ collisions at $\sqrt{s}=$ s=630 and 1800 GeV

The production cross section for isolated photons in pp̄ collisions at s = 630 GeV was measured and compared with that measured at s = 1800 GeV. It was found that the measurement is higher than the theoretical prediction at low E T in the central rapidity region but agrees at all other E T and in the forward rapidity region. Furthermore, it was observed that the difference between data and theory is less significant for the ratio of cross sections, and the theory is consistent with the data over all E T.