Violation of sum rules for twist-3 parton distributions in QCD

Sum rules for twist-3 distributions are reexamined. Integral relations between twist-3 and twist-2 parton distributions suggest the possibility for a delta-function at x = 0. We confirm and clarify this result by constructing h(L) and h(L)(3) (quark-gluon interaction dependent part of h(L)) explicitly from their moments for a one-loop dressed massive quark. The physics of these results is illustrated by calculating h(L) (x, Q(2)) using light-front time-ordered pQCD to O(alpha(S)) on a quark target. A delta(x) term is also found in e(x, Q(2)), but not in g(T) (x, Q(2)), to this order in O(alpha(S)). (C) 2002 Elsevier Science B.V. All rights reserved.