Observation of isolated high-E_T photons in deep inelastic scattering

TL;DR

This paper reports the first measurements of isolated prompt photon production cross sections in deep inelastic ep scattering at HERA, providing new experimental data and comparing it with theoretical calculations.

Contribution

It presents the first experimental measurements of isolated prompt photon cross sections in deep inelastic scattering and compares them with next-to-leading order QCD calculations.

Findings

Measured cross sections for isolated photons and associated jets.

Data agrees reasonably well with theoretical predictions.

Provides new insights into photon production mechanisms in DIS.

Abstract

First measurements of cross sections for isolated prompt photon production in deep inelastic ep scattering have been made using the ZEUS detector at the HERA electron-proton collider using an integrated luminosity of 121 pb^-1. A signal for isolated photons in the transverse energy and rapidity ranges 5 < E_T^gamma < 10 GeV and -0.7 < eta^gamma < 0.9 was observed for virtualities of the exchanged photon of Q^2 > 35 GeV^2. Cross sections are presented for inclusive prompt photons and for those accompanied by a single jet in the range E_T^jet \geq 6 GeV and -1.5 \leq eta^jet < 1.8. Calculations at order alpha^3alpha_s describe the data reasonably well.