Inclusive dijet cross sections in neutral current deep inelastic scattering at HERA

TL;DR

The paper addresses precision tests of perturbative QCD in neutral-current deep inelastic scattering by measuring inclusive dijet cross sections at high $Q^2$ with the ZEUS detector at HERA. A Breit-frame, $k_T$ jet analysis is performed on data corresponding to 374 pb$^{-1}$, with jets required to satisfy $E^{\rm jet}_{T,{\rm B}} > 8$ GeV and $M_{jj} > 20$ GeV, and cross sections are compared to NLO QCD predictions using CTEQ6.6 PDFs and hadronisation corrections. The authors assess both experimental and theoretical uncertainties, including jet and electron energy scales, QED radiative effects, MC-model dependence, and PDF variations, and find generally good agreement between data and theory across multiple observables. The results provide stringent tests of pQCD and supply valuable constraints for determinations of the strong coupling constant $\alpha_s$ and the proton PDFs, particularly the gluon density at large $x$, thereby contributing to precision QCD phenomenology and global PDF fits.

Abstract

Single- and double-differential inclusive dijet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 374 pb^-1. The measurement was performed at large values of the photon virtuality, Q^2, between 125 and 20000 GeV^2. The jets were reconstructed with the k_T cluster algorithm in the Breit reference frame and selected by requiring their transverse energies in the Breit frame, E_T,B^jet, to be larger than 8 GeV. In addition, the invariant mass of the dijet system, M_jj, was required to be greater than 20 GeV. The cross sections are described by the predictions of next-to-leading-order QCD.

Figures (14)

• Figure 1: Uncorrected data distributions for inclusive dijet production (dots). For comparison, the predictions of the ARIADNE (dashed histograms) and LEPTO (solid histograms) MC models are also included.
• Figure 2: Comparison of uncorrected data (dots) and MC model predictions for distributions of $\mathit{\log_{10}\left(\xi\right)}$ in different regions of $\mathit{Q^2}$. For comparison, the predictions of the ARIADNE (dashed histograms) and LEPTO (solid histograms) MC models are also included.
• Figure 3: Comparison of uncorrected data (dots) and MC model predictions for distributions of $\mathit{\overline{E^{\rm jet}_{T,{\rm B}}}}$ in different regions of $\mathit{Q^2}$. For comparison, the predictions of the ARIADNE (dashed histograms) and LEPTO (solid histograms) MC models are also included.
• Figure 4: The fraction of gluon-induced events as a function of $\mathit{\log_{10}\left(\xi\right)}$ as predicted by the CTEQ6.6 PDFs in different regions of $\mathit{Q^2}$.
• Figure 5: The fraction of gluon-induced events as a function of $\mathit{\overline{E^{\rm jet}_{T,{\rm B}}}}$ as predicted by the CTEQ6.6 PDFs in different regions of $\mathit{Q^2}$.