Evolution of the spin of the nucleon

Abstract

We compare momentum sum rules from unpolarized electroproduction and the spin sum rule for $g_1$ in polarized electroproduction, and their $Q^2$ evolution in the framework of the operator product expansion. Second order effects in $α_s$ are included. We show that in comparing the evolution of the spin sum rule with the momentum sum rule one is not overly sensitive to using first or second order, even when going to the extreme low $Q^2$ limit in which gluons carry no momentum. Our results show that in that limit there is no need to include any contribution of strange quarks.