Unifying the landscape of nucleon structure: an infrared-safe evolution scheme

TL;DR

This paper introduces an infrared-safe evolution scheme for nucleon structure that incorporates emergent hadron mass effects and parton recombination, providing a unified description across all energy scales.

Contribution

It presents a novel evolution scheme that accounts for low-$Q^2$ effects and yields consistent parton distributions across the entire $Q^2$ spectrum.

Findings

Parton distributions freeze at low $Q^2$ due to effective parton mass.

Recombination effects suppress small-$x$ growth, matching experimental data.

Scheme achieves good agreement with deep-inelastic scattering data.

Abstract

A novel approach for describing the evolution of nucleon structure from the low-$Q^2$ regime to the high-$Q^2$ asymptotic region is proposed. This infrared-safe scheme modifies the parton distribution evolution equations to incorporate the corrections from emergent hadron mass mechanisms and parton-parton recombination at low $Q^2$. The effective parton mass, generated by dynamical chiral symmetry breaking, slows the evolution of parton distributions in the infrared region, causing the DGLAP evolution to freeze when $Q^2\ll M_{\rm q/g}$. Notably, this scheme renders the high-$Q^2$ parton distributions insensitive to the choice of input hadronic scale. The parton-parton recombination effect is crucial in suppressing the rapid growth of parton distributions at small $x$, consistent with experimental data. When applied to three valence quark distributions derived from a quark model, our scheme yields parton distributions that agree well with deep-inelastic scattering data in both large-$x$ and small-$x$ regions, providing a unified description of nucleon structure across the entire $Q^2$ range.