Comparison of the isolated direct photon cross sections in pp̄ collisions at √s = 1.8 TeV and √s = 0.63 TeV

D. Acosta, T. Affolder, H. Akimoto, M. G. Albrow, D. Ambrose, D. Amidei, K. Anikeev, J. Antos, G. Apollinari, T. Arisawa, A. Artikov, T. Asakawa, W. Ashmanskas, F. Azfar, P. Azzi-Bacchetta, N. Bacchetta, H. Bachacou, W. Badgett, S. Bailey, P. De BarbaroA. Barbaro-Galtieri, V. E. Barnes, B. A. Barnett, S. Baroiant, M. Barone, G. Bauer, F. Bedeschi, S. Belforte, W. H. Bell, G. Bellettini, J. Bellinger, D. Benjamin, J. Bensinger, A. Beretvas, J. P. Berge, J. Berryhill, A. Bhatti, M. Binkley, D. Bisello, M. Bishai, R. E. Blair, C. Blocker, K. Bloom, B. Blumenfeld, S. R. Blusk, A. Bocci, A. Bodek, G. Bolla, Y. Bonushkin, D. Bortoletto, J. Boudreau, A. Brandl, S. Van Den Brink, C. Bromberg, M. Brozovic, E. Brubaker, N. Bruner, J. Budagov, H. S. Budd, K. Burkett, G. Busetto, A. Byon-Wagner, K. L. Byrum, S. Cabrera, P. Calafiura, M. Campbell, W. Carithers, J. Carlson, D. Carlsmith, W. Caskey, A. Castro, D. Cauz, A. Cerri, A. W. Chan, P. S. Chang, P. T. Chang, J. Chapman, C. Chen, Y. C. Chen, M. T. Cheng, M. Chertok, G. Chiarelli, I. Chirikov-Zorin, G. Chlachidze, F. Chlebana, L. Christofek, M. L. Chu, J. Y. Chung, W. H. Chung, Y. S. Chung, C. I. Ciobanu, A. G. Clark, M. Coca, A. P. Colijn, A. Connolly, M. Convery, J. Conway, M. Cordelli, J. Cranshaw

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66 Scopus citations

Abstract

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.

Original languageEnglish (US)
Article number112003
JournalPhysical Review D
Volume65
Issue number11
DOIs
StatePublished - 2002
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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