Measurement of isolated photons accompanied by jets in deep inelastic ep scattering

TL;DR

This paper reports measurements of isolated high-energy photons with jets in deep inelastic ep scattering at HERA, comparing results with perturbative QCD predictions and highlighting discrepancies in normalization.

Contribution

First measurement of isolated photon plus jet production in deep inelastic ep scattering at HERA with detailed differential cross sections.

Findings

Perturbative QCD describes the shape of the data well.

Normalisation of QCD predictions differs by 20-30%.

Data covers a wide kinematic range of photon and jet energies.

Abstract

The production of isolated high-energy photons accompanied by jets has been measured in deep inelastic ep scattering with the ZEUS detector at HERA, using an integrated luminosity of 326 pb^{-1}. Measurements were made for exchanged photon virtualities, Q^2, in the range 10 to 350 GeV^2. The photons were measured in the transverse-energy and pseudorapidity ranges 4 < ET^gamma < 15 GeV and -0.7 < eta^gamma < 0.9, and the jets were measured in the transverse-energy and pseudorapidity ranges 2.5 < ET^jet <35 GeV and -1.5 < eta^jet < 1.8. Differential cross sections are presented as functions of these quantities. Perturbative QCD predictions give a reasonable description of the shape of the measured cross sections over most of the kinematic range, but the absolute normalisation is typically in disagreement by 20-30%.