High-E_T Inclusive Jet Cross Sections in Photoproduction at HERA

TL;DR

This paper reports measurements of inclusive jet cross sections in photoproduction at HERA, comparing results with NLO QCD calculations, revealing good agreement for certain jet definitions and discrepancies at high pseudorapidity.

Contribution

First detailed measurement of inclusive jet cross sections in photoproduction at HERA across multiple cone sizes and energies, with comparison to NLO QCD calculations highlighting areas of agreement and discrepancy.

Findings

Data agrees with NLO QCD for R=0.7 across all ranges.

Discrepancies observed at high eta(jet) for R=1.0.

Cross section varies linearly with cone radius R.

Abstract

Inclusive jet differential cross sections for the reaction e+ p --> e+ + jet + X with quasi-real photons have been measured with the ZEUS detector at HERA. These cross sections are given for the photon-proton centre-of-mass energy interval 134 < W < 277 GeV and jet pseudorapidity in the range -1 < eta(jet) < 2 in the laboratory frame. The results are presented for three cone radii in the eta-phi plane, R=1.0, 0.7 and 0.5. Measurements of dsigma/deta(jet) above various jet-transverse-energy thresholds up to 25 GeV and in three ranges of W are presented and compared to next-to-leading order (NLO) QCD calculations. For jets defined with R=1.0 differences between data and NLO calculations are seen at high eta(jet) and low E_T(jet). The measured cross sections for jets defined with R=0.7 are well described by the calculations in the entire measured range of eta(jet) and E_T(jet). The inclusive jet cross section for E_T(jet) > 21 GeV is consistent with an approximately linear variation with the cone radius R in the range between 0.5 and 1.0, and with NLO calculations.