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

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

We have measured the cross sections d2σ/d P Tdη) for production of isolated direct photons in pp̄ 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 chromodynam...

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Bibliographic Details
Main Authors: Acosta, D, Affolder, T, Akimoto, H, Albrow, MG, Ambrose, D, Amidei, D, Anikeev, K, Antos, J, Apollinari, G, Arisawa, T, Artikov, A, Asakawa, T, Ashmanskas, W, Azfar, F, Azzi-Bacchetta, P, Bacchetta, N, Bachacou, H, Badgett, W, Bailey, S, de Barbaro, P, Barbaro-Galtieri, A, Barnes, V, Barnett, B, Baroiant, S, Barone, M
Format: Journal article
Language:English
Published: 2002
Description
Summary:We have measured the cross sections d2σ/d P Tdη) for production of isolated direct photons in pp̄ 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 (PT) of 25 GeV/c, but the shapes versus photon PT do not. These shape differences lead to a significant disagreement in the ratio of cross sections in the scaling variable xT(≡ 2PT/√s). This disagreement in the xT ratio is difficult to explain with conventional theoretical uncertainties such as scale dependence and parton distribution parametrizations. © 2002 The American Physical Society.

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