Inclusive-jet and dijet cross sections in deep inelastic scattering at HERA

TL;DR

The paper measures inclusive-jet and dijet cross sections in neutral-current deep inelastic scattering at high $Q^2$ with ZEUS at HERA, using jets in the Breit frame identified by the $k_T$ algorithm. It compares the results to next-to-leading-order QCD predictions with hadronization and radiative corrections, finding good agreement and identifying regions where theoretical uncertainties are small. The study highlights the sensitivity of the data to the gluon density in the proton, and demonstrates the potential of these measurements to constrain PDFs in global fits. The work extends the kinematic reach and provides precision data to refine our understanding of proton structure and QCD dynamics in DIS.

Abstract

Inclusive-jet and dijet differential cross sections have been measured in neutral current deep inelastic ep scattering for exchanged boson virtualities Q2 > 125 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 82 pb-1. Jets were identified in the Breit frame using the kt cluster algorithm. Jet cross sections are presented as functions of several kinematic and jet variables. The results are also presented in different regions of Q2. Next-to-leading-order QCD calculations describe the measurements well. Regions of phase space where the theoretical uncertainties are small have been identified. Measurements in these regions have the potential to constrain the gluon density in the proton when used as inputs to global fits of the proton parton distribution functions.

Figures (12)

• Figure 1: Uncorrected data distributions for dijet production with $E^{\rm jet1}_{T,{\rm B}}>12$GeV, $E^{\rm jet2}_{T,{\rm B}}>8$GeV and $-2<\eta^{\rm jet}_{\rm B}<1.5$ in the kinematic range given by $|{\rm cos} \gamma_h| <$ 0.65 and 125 $< Q^2 <$ 5000 ${\rm GeV^2}$ (dots). For comparison, the predictions of the ARIADNE (dashed histograms) and LEPTO (solid histograms) MC models are also included.
• Figure 2: Overview of theoretical uncertainties for the inclusive-jet analysis as functions of $E^{\rm jet}_{T,{\rm B}}$ in bins of $Q^2$ for $|{\rm cos} \gamma_h| <$ 0.65 and $-2<\eta^{\rm jet}_{\rm B}<1.5$. Shown are the relative uncertainties induced by the variation of the renormalisation scale $\mu_R$ (hatched area) and by the uncertainties on the proton PDFs (shaded area).
• Figure 3: Overview of theoretical uncertainties for the dijet analysis as functions of $\log_{10}\xi$ in bins of $Q^2$ for $|{\rm cos} \gamma_h| <$ 0.65, $E_{T,{\rm B}}^{jet1} >$ 12 GeV, $E_{T,{\rm B}}^{jet2} >$ 8 GeV and $-2<\eta^{\rm jet}_{\rm B}<1.5$. Other details as in the caption to Fig. \ref{['fig11']}.
• Figure 4: NLO QCD predictions of the gluon-induced fraction of the inclusive-jet cross sections $d\sigma/dE^{\rm jet}_{T,{\rm B}}$ as functions of $E_{T,B}^{jet}$ in different regions of $Q^2$ for $|{\rm cos} \gamma_h| <$ 0.65 and $-2<\eta^{\rm jet}_{\rm B}<1.5$ (shaded histograms). The CTEQ6 parameterisations of the proton PDFs were used.
• Figure 5: NLO QCD predictions of the gluon-induced fraction of the dijet cross-sections $d\sigma/d\log_{10}\xi$ as functions of $\log_{10}\xi$ in different regions of $Q^2$ for $|{\rm cos} \gamma_h| <$ 0.65, $E_{T,{\rm B}}^{jet1} >$ 12 GeV, $E_{T,{\rm B}}^{jet2} >$ 8 GeV and $-2<\eta^{\rm jet}_{\rm B}<1.5$. Other details as in the caption to Fig. \ref{['gluefrac1']}.