Abstract
We have measured the cross sections for production of isolated direct photons in collisions at two different center-of-mass energies, 1.8 TeV and 0.63 TeV, using the Collider Detector at Fermilab. The normalization of both data sets agrees with the predictions of quantum chromodynamics for a photon transverse momentum of 25 GeV/c, but the shapes versus photon do not. These shape differences lead to a significant disagreement in the ratio of cross sections in the scaling variable This disagreement in the ratio is difficult to explain with conventional theoretical uncertainties such as scale dependence and parton distribution parametrizations.
- Received 5 January 2002
DOI:https://doi.org/10.1103/PhysRevD.65.112003
©2002 American Physical Society