Fock Space Distributions , Structure Functions , Higher Twists and Small x

We compute quark structure functions and the intrinsic Fock space distribution of sea quarks in a hadron wavefunction at small x. The computation is performed in an effective theory at small x where the gluon field is treated classically. At Q2 large compared to an intrinsic scale associated with the density of gluons μ2, large compared to the QCD scale ΛQCD, and large compared to the quark mass squared M2, the Fock space distribution of quarks is identical to the distribution function measured in deep inelastic scattering. For Q2 ≤ M2 but Q2 >> μ2, the quark distribution is computed in terms of the gluon distribution function and explicit expressions are obtained. For Q2 ≤ μ2 but Q2 >> ΛQCD we obtain formal expressions for the quark distribution functions in terms of the glue. An evaluation