Comparison of the isolated direct photon cross sections in p(p)over-bar collisions at root s=1.8 TeV and root s=0.63 TeV

Acosta D., Affolder T., Akimoto H., Albrow M., Ambrose D., Amidei D., ...Daha Fazla

PHYSICAL REVIEW D, cilt.65, 2002 (SCI İndekslerine Giren Dergi) identifier


We have measured the cross sections d(2)sigma/dP(T)deta for production of isolated direct photons in p (p) over bar 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 (P-T) of 25 GeV/c, but the shapes versus photon P-T do not. These shape differences lead to a significant disagreement in the ratio of cross sections in the scaling variable x(T)(=2P(T)/roots). This disagreement in the x(T) ratio is difficult to explain with conventional theoretical uncertainties such as scale dependence and parton distribution parametrizations.