QCD Analysis of Twist-4 Contributions to the g₁ Structure Functions

We analyze the twist-4 contributions to Bjorken and Ellis-Jaffe sum rules for spin-dependent structure function $g_1(x, Q^2 )$. We investigate the anomalous dimensions of the twist-4 operators which determine the logarithmic correction to the $1/Q^2$ behavior of the twist-4 contribution by evaluating off-shell Green's functions in both flavor non-singlet and singlet case. It is shown that the EOM operators play an important role to extract the anomalous dimensions of physical operators. The calculations to solve the operator mixing of higher-twist operators are given in detail.