Combination of measurements of inclusive deep inelastic $${e^{\pm }p}$$ e ± p scattering cross sections and QCD analysis of HERA data

TLDR

The study combines all inclusive deep‑inelastic e±p scattering cross sections from H1 and ZEUS at HERA, extending the analysis to include charm and jet production data to produce the HERAPDF2.0 parton distribution functions. Using data taken at proton energies of 920–460 GeV and an electron energy of 27.5 GeV, with ~1 fb⁻¹ integrated luminosity and systematic uncertainty correlations, the authors performed LO, NLO, and NNLO QCD fits to derive HERAPDF2.0 and its variants, incorporating model and parameterisation uncertainties and jet‑production cross sections for simultaneous PDF and αs determination. The resulting HERAPDF2.0 set, including HERAPDF2.0AG, HERAPDF2.0FF, and HERAPDF2.0Jets, yields αs(MZ²)=0.1183 ± 0.0009(exp) ± 0.0005(model) ± 0.0012(hadronisation) +0.0037/−0.0030(scale) and provides an extraction of xF3^γZ, confirming electroweak unification and scaling violations.

Abstract

A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current $$e^{\pm }p$$ scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb $$^{-1}$$ and span six orders of magnitude in negative four-momentum-transfer squared, $$Q^2$$ , and Bjorken x. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in $$\alpha _s(M_Z^2)=0.1183 \pm 0.0009 \mathrm{(exp)} \pm 0.0005\mathrm{(model/parameterisation)} \pm 0.0012\mathrm{(hadronisation)} ^{+0.0037}_{-0.0030}\mathrm{(scale)}$$ . An extraction of $$xF_3^{\gamma Z}$$ and results on electroweak unification and scaling violations are also presented.