High-energy resummation of direct photon production at hadronic colliders

Direct photon production is an important process at hadron colliders, being relevant
both for precision measurement of the gluon density, and as background to Higgs and other
new physics searches. Here we explore the implications of recently derived results for high
energy resummation of direct photon production for the interpretation of measurements
at the Tevatron and the LHC. The effects of resummation are compared to various sources
of theoretical uncertainties like PDFs and scale variations. We show how the high–energy
resummation procedure stabilizes the logarithmic enhancement of the cross section at
high–energy which is present at any fixed order in the perturbative expansion starting at
NNLO. The effects of high–energy resummation are found to be negligible at Tevatron,
while they enhance the cross section by a few percent for pT < 10 GeV at the LHC. Our
∼
results imply that the discrepancy at small pT between fixed order NLO and Tevatron
data cannot be explained by unresummed high–energy contributions.