Study of non-collinear parton dynamics in the prompt photon photoproduction at HERA

TL;DR

This paper analyzes prompt photon production at HERA using kt-factorization QCD, comparing theoretical predictions with experimental data and exploring the role of different unintegrated parton densities and kinematic properties.

Contribution

It introduces a detailed study of non-collinear parton dynamics in prompt photon photoproduction using KMR and CCFM unintegrated parton densities, with comprehensive error analysis.

Findings

Theoretical results agree with H1 and ZEUS data.

Quark contributions from earlier evolution steps are about 15-20%.

Photon-jet kinematic properties are highly sensitive to parton transverse momentum.

Abstract

We investigate the prompt photon photoproduction at HERA within the framework of kt-factorization QCD approach. Our consideration is based on the off-shell matrix elements for the underlying partonic subprocesses. The unintegrated parton densities in a proton and in a photon are determined using the Kimber-Martin-Ryskin (KMR) prescription. Additionally, we use the CCFM-evolved unintegrated gluon as well as valence and sea quark distributions in a proton. A conservative error analisys is performed. Both inclusive and associated with the hadronic jet production rates are investigated. The theoretical results are compared with the recent experimental data taken by the H1 and ZEUS collaborations. We study also the specific kinematical properties of the photon-jet system which are strongly sensitive to the transverse momentum of incoming partons. Using the KMR scheme, the contribution from the quarks emerging from the earlier steps of the parton evolution is estimated and found to be of 15 - 20 approximately.