Global fits of proton PDFs with non-linear corrections from gluon recombination

TL;DR

This paper investigates non-linear gluon recombination effects on proton PDFs at small x, implementing corrections in evolution equations, fitting to experimental data, and assessing future collider measurements' impact.

Contribution

It introduces numerical implementation of non-linear corrections in PDF evolution and evaluates their significance using existing data and future collider projections.

Findings

No evidence for non-linear effects in current data.

Upper limits established for non-linear correction strength.

Future collider measurements could improve constraints.

Abstract

We present numerical studies of the leading non-linear corrections to the DGLAP evolution equations of parton distribution functions (PDFs) resulting from gluon recombination, which reduce the pace of evolution at small momentum fractions $x$. The non-linear evolution is implemented in the \textsc{HOPPET} and \textsc{xFitter} toolkits and used to carry out fits of proton PDFs using lepton-proton deep inelastic scattering data from HERA, BCDMS and NMC. While we do not find evidence for non-linear effects, we are able to set upper limits for their strength. We also quantify the potential impact of longitudinal structure function measurements at the Electron-Ion Collider and the Large Hadron Electron Collider on future fits.