QCD sum rule calculation of twist-4 corrections to Bjorken and Ellis-Jaffe sum rules

We calculate the twist-4 corrections to the integral of g_1(x,Q^2) in the framework of QCD sum rules using an interpolating nucleon field which contains explicitly a gluonic degree of freedom. This information can be used together with previous calculations of the twist-3 contribution to the second moment of g_2(x) to estimate the higher-twist corrections to the Ellis-Jaffe and Bjorken sum rules. We get f^{(2)}(proton) = -0.037 \pm 0.006 and f^{(2)}(neutron) = -0.013 \pm 0.006. Numerically our results roughly agree with those obtained by Balitsky, Braun and Kolesnichenko based on a sum rule for a simpler current. Our calculations are far more stable as tested within the sum rule approach but are more sensitive to less well known condensates