Jet-radius dependence of inclusive-jet cross sections in deep inelastic scattering at HERA

TL;DR

This paper measures how inclusive-jet cross sections in deep inelastic scattering depend on jet radius R, compares results with QCD predictions, and extracts the strong coupling constant alpha_s(M_Z) with high precision.

Contribution

It provides the first detailed study of jet radius dependence in inclusive-jet cross sections at HERA and extracts alpha_s(M_Z) from high-Q^2 data.

Findings

Cross section dependence on R is linear in studied range.

QCD calculations accurately describe the data for 0.5 <= R <= 1.

Alpha_s(M_Z) is measured as 0.1207 with uncertainties, consistent with QCD predictions.

Abstract

Differential inclusive-jet cross sections have been measured for different jet radii in neutral current deep inelastic ep scattering for boson virtualities Q^2 > 125 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb^-1. Jets were identified in the Breit frame using the k_T cluster algorithm in the longitudinally inclusive mode for different values of the jet radius R. Differential cross sections are presented as functions of Q^2 and the jet transverse energy, E_T,B^jet. The dependence on R of the inclusive-jet cross section has been measured for Q^2 > 125 and 500 GeV^2 and found to be linear with R in the range studied. Next-to-leading-order QCD calculations give a good description of the measurements for 0.5 <= R <= 1. A value of alpha_s(M_Z) has been extracted from the measurements of the inclusive-jet cross-section dsigma/dQ^2 with R=1 for Q^2 > 500 GeV^2: alpha_s(M_Z) = 0.1207 +- 0.0014 (stat.) -0.0033 +0.0035 (exp.) -0.0023 +0.0022 (th.). The variation of alpha_s with E_T,B^jet is in good agreement with the running of alpha_s as predicted by QCD.