Sum Rules for the Spin-Dependent StructureFunctions from the Current Algebra on theNull-Plane

摘要

Spin dependent sum rules from the current algebra on the null-plane both from the current commutation and the current anti-commutation relations are given. By regularizing these sum rules, we explain that the Born term, resonances and the continuum are constrained severely by the sum rules. This fact explains why the sign change of the Gerasimov-Drell-Hearn (GDH) sum occurs in the very small Q~2. Further, combined with the regularized Burkhart and Cottingham(BC) sum rule, we find that g_2~(ep) has a similar behavior as g_1~(ep). The method has been applied to the deuteron target.