Prompt Photons in Photoproduction at HERA

TL;DR

This paper reports the first measurements of isolated prompt photon production in photoproduction at HERA, comparing experimental data with theoretical models and highlighting areas of agreement and discrepancy.

Contribution

It provides the first inclusive measurements of isolated prompt photons in photoproduction at HERA and compares them with theoretical predictions.

Findings

Good agreement in the forward region with models

Models underestimate data in the rear direction

Provides new data for testing QCD predictions

Abstract

First inclusive measurements of isolated prompt photons in photoproduction at HERA have been made with the ZEUS detector. Cross sections are given as a function of the pseudorapidity and the transverse energy of the photon, for E_T^gamma > 5 GeV in the gamma-p centre-of-mass energy range 134-285 GeV. Comparisons are made with predictions from LO Monte Carlo models and NLO QCD calculations. For forward eta^gamma (proton direction) good agreement is found, but in the rear direction all predictions fall below the data.