High energy resummation of direct photon production at hadronic colliders

TL;DR

This paper investigates the impact of high-energy resummation on direct photon production at hadron colliders, showing it stabilizes predictions and slightly enhances the cross section at the LHC, but does not resolve existing discrepancies at Tevatron.

Contribution

It applies recent high-energy resummation techniques to direct photon production, providing a more stable theoretical prediction and quantifying their effects at Tevatron and LHC energies.

Findings

Resummation stabilizes the cross section at high energies.

Effects are negligible at Tevatron energies.

Enhancement of a few percent at the LHC for low transverse momentum.

Abstract

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 $p_T \lsim 10$ GeV at the LHC. Our results imply that the discrepancy at small $p_T$ between fixed order NLO and Tevatron data cannot be explained by unresummed high--energy contributions.