Spin dependent structure function g1. Recent experimental results

Abstract

In the last two years new measurements of the structure functions g 1 p, g 1 n, g 1 d have been performed by experiments at CERN, SLAC and DESY. A complete review of these experimental results is presented. Perturbative QCD evolution in next-to-leading order is used to evolve g 1 to a common Q 2, at which the first moment or the structure function is evaluated. Results from different experiments show consistently a violation of the Ellis-Jaffe sum rule. A preliminary combined analysis of all the available data gives at 5 GeV 2: Γ 1 p − Γ 1 n = ∫ 0 1 g 1 p( x) − ∫ 0 1 g 1 n( x) = 0.189 ± 0.018, in agreement with the theoretical prediction given by the Bjorken sum rule 0.181 ± 0.03.