Measurement of dijet production in neutral current deep inelastic scattering at high Q**2 and determination of alpha_s

TL;DR

This study measures dijet production in high-Q^2 neutral current deep inelastic scattering at HERA, using NLO QCD calculations to determine the strong coupling constant alpha_s(M_Z) with improved precision and testing its energy dependence.

Contribution

It provides a precise measurement of alpha_s(M_Z) from dijet data and assesses uncertainties from parton distribution functions, enhancing the understanding of QCD at high energies.

Findings

Measured dijet cross sections match NLO QCD predictions.

Determined alpha_s(M_Z) = 0.1166 with detailed uncertainty analysis.

Confirmed the energy-scale dependence of the strong coupling constant.

Abstract

Dijet production has been studied in neutral current deep inelastic e+p scattering for 470 < Q**2 < 20000 GeV**2 with the ZEUS detector at HERA using an integrated luminosity of 38.4 pb**{-1}. Dijet differential cross sections are presented in a kinematic region where both theoretical and experimental uncertainties are small. Next-to-leading-order (NLO) QCD calculations describe the measured differential cross sections well. A QCD analysis of the measured dijet fraction as a function of Q**2 allows both a precise determination of alpha_s(M_Z) and a test of the energy-scale dependence of the strong coupling constant. A detailed analysis provides an improved estimate of the uncertainties of the NLO QCD cross sections arising from the parton distribution functions of the proton. The value of alpha_s(M_Z), as determined from the QCD fit, is alpha_s(M_Z) = 0.1166 +- 0.0019 (stat.) {+ 0.0024}_{-0.0033} (exp.)} {+ 0.0057}_{- 0.0044} (th.).