Sea Quark or Anomalous Gluon Interpretation for g p 1(x)?

Contrary to what has been often claimed in the literature, we clarify that the hard photongluon cross section ∆σ hard(x) in polarized deep inelastic scattering calculated in the gauge-invariant factorization scheme does not involve any soft contributions and hence it is genuinely hard. We show that the polarized proton structure function g 1(x) up to the next-to-leading order of αs is independent of the factorization convention, e.g., the gauge-invariant or chiral-invariant scheme, chosen in defining ∆σ hard(x) and the quark spin density. Thereby, it is not pertinent to keep disputing which factorization prescription is correct or superior. The hard-gluonic contribution to Γp1, the first moment of g p 1(x), is purely factorization dependent. Nevertheless, we stress that even though hard gluons do not contribute to Γp1 in the gauge-invariant scheme, the gluon spin component in a proton, which is factorization independent, should be large enough to perturbatively generate a negative sea polarization via the axial anomaly. We briefly comment on how to study the Q2 evolution of parton spin distributions to the next-to-leading order of QCD in the chiral-invariant factorization scheme.