[formula presented] effects in direct-photon production

L. Apanasevich, C. Balázs, C. Bromberg, J. Huston, A. Maul, W. K. Tung

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We discuss the phenomenology of initial-state parton-(Formula presented) broadening in direct-photon production and related processes in hadron collisions. After a brief summary of the theoretical basis for a Gaussian-smearing approach, we present a systematic study of recent results on fixed-target and collider direct-photon production, using complementary data on diphoton and pion production that provide empirical guidance on the required amount of (Formula presented) broadening. This approach provides a consistent description of the observed pattern of deviation of next-to-leading order QCD calculations relative to the direct-photon data, and accounts for the shape and normalization difference between fixed-order perturbative calculations and the data. We also discuss the uncertainties in this phenomenological approach, the implications of these results on the extraction of the gluon distribution of the nucleon, and the comparison of our findings to recent related work.

Original languageEnglish
JournalPhysical Review D
Issue number7
Publication statusPublished - 18 Feb 1999
Externally publishedYes

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