Global QCD analysis of spin PDFs in the proton with high-$x$ and lattice constraints

TL;DR

This paper performs a comprehensive global analysis of spin-dependent PDFs in the proton, integrating diverse experimental data and lattice QCD constraints to improve understanding of the proton's spin structure, especially at high momentum fractions.

Contribution

It introduces a combined analysis of experimental and lattice data to refine polarized PDFs and assess higher twist effects, advancing the understanding of proton spin structure.

Findings

Improved constraints on polarized gluon PDF from lattice and experimental data.

Verification of the stability of PDFs for $W^2 \\geq 4$ GeV$^2$ with subleading power corrections.

Refined bounds on higher twist contributions and tests of the Bjorken sum rule.

Abstract

We perform a comprehensive global QCD analysis of spin-dependent parton distribution functions (PDFs), combining all available data on inclusive and semi-inclusive deep-inelastic scattering (DIS), as well as inclusive weak boson and jet production in polarized $pp$ collisions, simultaneously extracting spin-averaged PDFs and fragmentation functions. Including recent Jefferson Lab DIS data at high $x$, together with subleading power corrections to the leading twist framework, allows us to verify the stability of the PDFs for $W^2 \geq 4$ GeV$^2$ and quantify the uncertainties on the spin structure functions more reliably. We explore the use of new lattice QCD data on gluonic pseudo Ioffe-time distributions, which, together with jet production and high-$x$ DIS data, improve the constraints on the polarized gluon PDF. The expanded kinematic reach afforded by the data into the high-$x$ region allows us to refine the bounds on higher twist contributions to the spin structure functions, and test the validity of the Bjorken sum rule.