# First simultaneous extraction of spin-dependent parton distributions and fragmentation functions from a global QCD analysis

## TL;DR

This paper presents the first comprehensive global QCD analysis that simultaneously extracts spin-dependent parton distributions and fragmentation functions from diverse scattering data, resolving longstanding puzzles about strange quark polarization.

## Contribution

It introduces a novel simultaneous extraction method using Monte Carlo techniques, avoiding SU(3) symmetry assumptions, and provides new insights into strange quark polarization and axial charges.

## Key findings

- Strange polarization is consistent with zero.
- The analysis resolves the strange quark polarization puzzle.
- Results support a small SU(2) flavor asymmetry in the polarized sea.

## Abstract

We perform the first global QCD analysis of polarized inclusive and semi-inclusive deep-inelastic scattering and single-inclusive $e^+e^-$ annihilation data, fitting simultaneously the parton distribution and fragmentation functions using the iterative Monte Carlo method. Without imposing SU(3) symmetry relations, we find the strange polarization to be very small, consistent with zero for both inclusive and semi-inclusive data, which provides a resolution to the strange quark polarization puzzle. The combined analysis also allows the direct extraction from data of the isovector and octet axial charges, and is consistent with a small SU(2) flavor asymmetry of the polarized sea.