Combination and QCD Analysis of the HERA Inclusive Cross Sections

TL;DR

This paper presents a comprehensive QCD analysis of combined HERA inclusive cross-section data, resulting in improved parton distribution functions with enhanced precision, especially at high-x, and discusses the impact of new data and different theoretical orders.

Contribution

It introduces HERAPDF1.0 and HERAPDF1.5 sets based on combined HERA data, including HERA II, and compares NLO and NNLO fits, highlighting improvements and tensions in the PDFs.

Findings

HERAPDF1.0 provides a competitive NLO PDF set.

Inclusion of HERA II data improves high-x PDF precision.

NNLO fits describe the data less accurately than NLO fits.

Abstract

A QCD fit analysis to the combined HERA-I inclusive deep inelastic cross sections measured by the H1 and ZEUS collaborations for $e^\pm p$ scattering resulting into a competitive NLO PDF set, HERAPDF1.0 is presented. HERAPDF at NNLO fits are presented as well, resulting, however, in a worse description of the combined HERA data. In addition, a preliminary analysis including the HERA II measurements of lower proton-beam energies is performed. The effect of including the new data on the determination of HERA parton distribution functions is analysed, using fits similar to those performed for HERAPDF1.0. Some tension of the QCD fit with respect to the data is identified in the kinematic region of low $Q^2$ and low x. Finally, the QCD fit analysis of the combined HERA-I inclusive deep inelastic cross sections has been extended to include combined HERA II measurements at high $Q^2$. The effect of including these data on the determination of parton distribution functions is analysed, resulting into HERAPDF1.5. The precision of the new PDFs at high-x is considerably improved, particularly in the valence sector.