Spin Structure Functions

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: $$ΔΣ\equiv Δu + Δd + Δs = 0.27 \pm 0.11 $$ $$Δu = 0.82 \pm 0.04, Δd = -0.44 \pm 0.04,Δs = -0.11 \pm 0.04 $$ 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.