Proton Structure Functions from Chiral Dynamics and QCD Constraints

The spin fractions and deep inelastic lepton structure functions of the proton are analyzed using chiral field theory involving Goldstone bosons. A detailed comparison with recent chiral models sheds light on their successful description of the spin fractions of the proton as being due to neglecting helicity non-flip chiral transitions. This approximation is valid for zero mass but not for constituent quarks. Since the chiral spin fraction models with the pure spin-flip approximation reproduce the measured spin fractions of the proton, axialvector constituent-quark-Goldstone boson couplings are found to be inconsistent with the proton spin data. Initial quark valence distributions are then constructed using quark counting constraints at Bjorken x →1 and Regge behavior at x → 0. Sea quark distributions predicted by chiral field theory on this basis have correct order of magnitude and shape. The spin fractions also agree with the data. PACS numbers: 11.30.Rd, 12.39.Fe, 14.20.Dh