Dijet Cross Sections in Photoproduction at HERA

TL;DR

This study measures dijet production in photoproduction at HERA, analyzing how cross sections depend on pseudorapidity and parton distributions in the proton and photon, using the ZEUS detector and cone algorithm.

Contribution

It provides new measurements of dijet cross sections sensitive to gluon distributions in the proton and photon, comparing results to leading order QCD calculations.

Findings

Cross sections vary with pseudorapidity for different xg regions.

Results are consistent with QCD predictions within uncertainties.

Gluon density in the proton and photon is probed through these measurements.

Abstract

Dijet production by almost real photons has been studied at HERA with the ZEUS detector. Jets have been identified using the cone algorithm. A cut on xg, the fraction of the photon energy participating in the production of the two jets of highest transverse energy, is used to define cross sections sensitive to the parton distributions in the proton and in the photon. The dependence of the dijet cross sections on pseudorapidity has been measured for xg $\ge 0.75$ and xg $< 0.75$. The former is sensitive to the gluon momentum density in the proton. The latter is sensitive to the gluon in the photon. The cross sections are corrected for detector acceptance and compared to leading order QCD calculations.