Spin structure of the nucleon - experimental results

The experimental status of the spin-dependent structure functions as obtained from deep inelastic scattering experiments at CERN, SLAC and DESY is discussed. The data available for gp1, gd1 and gn1 are evolved to common Q2 = 5 GeV2 and compared. The g1 structure functions are now precise enough to perform sensible QCD analysis. The predicted Q2 dependence from this analysis is used to evaluate g1(x) at common Q2, at which the first moment of g1 is calculated. The extrapolation of g1 to x = 0, which is a controversial issue, is discussed in some details. The results obtained in all experiments show that the Ellis-Jaffe sum rule is violated, consistent with previous observations. For the Bjorken sum rule we obtain: Γp -Γn ∫01 gp1(x, Q02) dx - ∫01 gn1(x, Q02) dx 0.192±0.021, which is in good agreement with the prediction of 0.181±0.003. (orig.)