Gluon contribution to the structure function g2(x,Q2) Origin

We calculate the one-loop twist-3 gluon contribution to the flavor-singlet structure function g2(x,Q2) in polarized deep-inelastic scattering and find that it is dominated by the contribution of the three-gluon operator with the lowest anomalous dimension (for each moment N). The similar property was observed earlier for the nonsinglet distributions, although the reason is in our case different. The result is encouraging and suggests a simple evolution pattern of g2(x,Q2) in analogy with the conventional description of twist-2 parton distributions.