Spin Structure Functions

TL;DR

This paper reviews the theory and recent experimental data on the spin structure functions of nucleons, confirming the Bjorken sum rule and providing updated values for quark spin contributions.

Contribution

It incorporates higher-order QCD corrections and new experimental data to refine the understanding of nucleon spin structure and quark contributions.

Findings

Good agreement with the Bjorken sum rule

Extracted quark spin contributions: ΔΣ=0.27±0.11

Values for Δu, Δd, Δs consistent with models

Abstract

We review the theory and phenomenology of deep inelastic polarized lepton-nucleon scattering in the light of recent data with a deuteron target from the SMC at CERN and a Helium 3 target from the E142 experiment at SLAC. After including higher-order perturbative QCD corrections, mass corrections and updated estimates of higher-twist effects, we find good agreement with the basic Bjorken sum rule, and extract a consistent set of values for the quark contributions to the proton spin: $$\Delta\Sigma \equiv \Delta u + \Delta d + \Delta s = 0.27 \pm 0.11 $$ $$\Delta u = 0.82 \pm 0.04, \Delta d = -0.44 \pm 0.04,\Delta s = -0.11 \pm 0.04 $$ which are consistent with chiral soliton models and indications from lattice estimates. We also mention the prospects for future experiments on the spin structure of the nucleon.