The Angular Momentum and g_1^p Sum Rules for the Proton

Abstract

The gauge invariant operator formulation of the angular momentum sum rule ${1\over2} = J_q + J_g$ for the proton is presented and contrasted with the sum rule for the first moment of the polarised structure function $g_1^p$. The decoupling of the axial charge $a^0$ from the angular momentum sum rule is highlighted and the possible QCD field-theoretic basis for an angular momentum sum rule of the form ${1\over2} = {1\over2}\D q + \D g + L_q + L_g$ is critically discussed.