Measurement of isolated photon production in deep inelastic ep scattering

TL;DR

This paper reports measurements of isolated photon production in deep inelastic electron-proton scattering at HERA, comparing results with theoretical predictions to test QCD models.

Contribution

First measurement of isolated photon production in deep inelastic ep scattering over a wide kinematic range at HERA.

Findings

Data generally agree with perturbative QCD predictions.

Monte Carlo simulations provide a reasonable description of the measurements.

Results help constrain models of photon production in QCD processes.

Abstract

Isolated photon production in deep inelastic ep scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 320pb^-1. Measurements were made in the isolated-photon transverse-energy and pseudorapidity ranges 4 < E_T < 15 GeV and -0.7 < eta < 0.9 for exchanged photon virtualities, Q^2, in the range 10 < Q^2 < 350 GeV and for invariant masses of the hadronic system W_X> 5 GeV. Differential cross sections are presented for inclusive isolated photon production as functions of Q^2, x, E_T and eta. Leading-logarithm parton-shower Monte Carlo simulations and perturbative QCD predictions give a reasonable description of the data over most of the kinematic range.