ORIGIN OF DIFFERENCE BETWEEN (U)OVER-BAR AND (D)OVER-BAR PARTONS IN THE NUCLEON

Using the Euclidean path-integral formulation for the hadronic tensor, we show that the large difference between uBAR and dBAR does not come from the disconnected quark-loop insertion. Rather, it can come from the connected (quark line) insertion involving quarks propagating back wards in time. We study the influence of the backward time propagator in the axial-vector and scalar matrix elements in lattice gauge calcul ations and give an estimate of the violation of the Gottfried sum rule .