Off-shell effects in bound nucleons and parton distributions from $^1$H, $^2$H, $^3$H and $^3$He data

TL;DR

This paper presents a comprehensive global QCD analysis of deep-inelastic scattering data from hydrogen and light nuclei, focusing on off-shell effects in bound nucleons and their impact on parton distributions.

Contribution

It introduces a nuclear convolution approach with off-shell corrections into a global fit, constraining nuclear effects alongside PDFs and higher-twist terms, and explores their implications for nucleon structure.

Findings

Off-shell corrections are consistent across proton and neutron with recent data.

Predictions for the neutron-to-proton structure function ratio $F_2^n/F_2^p$ are provided.

The analysis clarifies the relationship between nuclear effects and parton distribution ratios.

Abstract

We report the results of a new global QCD analysis including deep-inelastic scattering data off $^1$H, $^2$H, $^3$H, and $^3$He targets. Nuclear corrections are treated in terms of a nuclear convolution approach with off-shell bound nucleons. The off-shell (OS) corrections responsible for the modification of the structure functions (SFs) of bound nucleons are constrained in a global fit along with the proton parton distribution functions (PDFs) and the higher-twist (HT) terms. We investigate the proton-neutron difference for the OS correction and discuss our predictions for the SF ratio $F_2^n/F_2^p$ and the corresponding PDF ratio $d/u$ in the proton, as well as their correlations with the underlying treatment of the HT terms and of the OS corrections. In particular, we find that the recent MARATHON data are consistent with equal relative OS corrections for both the proton and the neutron.