Q(2) DEPENDENCE OF THE SUM-RULES FOR THE STRUCTURE FUNCTIONS OF POLARIZED E(MU)N SCATTERING

The nonperturbative Q(2) dependence of the sum rules for the structure functions of polarized e(mu)N scattering is discussed. The determinat ion of twist-4 corrections to the structure functions at high Q(2) by QCD sum rules is reviewed and critically analyzed. It is found that, i n the case of the Bjorken sum rule, the twist-4 correction is small fo r Q(2) > 5 GeV2 and does not affect the value of alpha(s) determined f rom this sum rule. However, the accuracy of current experimental data is insufficient for determining reliably alpha(s) from the Bjorken sum rule. For the singlet sum rule for the p + rt system, the QCD sum rul e yields only an order-of-magnitude estimate for the twist-4 correctio n. At low and intermediate Q(2), a model is proposed that implements a smooth connection between the Gerasimov-Drell-Hearn sum rules gr Q(2) = 0 and the sum rules far Gamma(p,n)(Q(2)) at high Q(2). The model is in good agreement with experimental data.