Photon plus jet cross sections in deep inelastic ep collisions at order O(α2α)

Abstract

The production of a hard and isolated photon accompanied by one or two jets in large-Q 2 deep inelastic ep scattering is calculated at next-to-leading order. We include consistently contributions from quark-to-photon fragmentation and study various differential cross sections and their dependence on isolation cut parameters. Numerical results relevant for HERA experiments are presented.

Photon–jet cross sections in deep-inelastic scattering

“…Large-p ⊥ photons have also been observed, in an inclusive way [1,2] or in correlation with a hadronic jet [1,3]. This latter reaction has been the subject of theoretical studies some ten years ago [4,5]. The recent data from ZEUS [3] lead us to extend these studies and to compare the complete NLO QCD results with the γ -jet cross sections.…”

“…The large p * ⊥ of the final photon provides the scale which can be compared with the photon virtuality; a large ratio p * 2 ⊥ /Q 2 defines the kinematical range in which the photon structure function formalism is useful. Such an approach, but without the introduction of the virtual-photon structure function, can be found in [4]. It contains detailed studies on the jet algorithms and the scale choice dependence of the cross sections.…”

Prompt Photon Production at Hera and Lep

“…In addition to the prompt photon a jet is required (E jet T > 6 GeV and −1.5 < η jet < 1.8). A pQCD calculation 16 to order O(α 3 α 1 s ) on parton level describes the normalisation of the data rather well. However, the description of the shape is poor at low E T and in the more forward (proton beam) direction.…”

Isolated photons in deep inelastic scattering and photoproduction

“…Systematic uncertainties are dominated by the photon and jet energy scales, and the modelling of the background. Comparison is made with the perturbative NLO QCD model of Gehrmann-de Ridder et al [8] and the model of Baranov et al [9], in which unintegrated parton densities are used in a LO QCD framework. The data and the theory predictions are corrected to the hadron level.…”