Sea Quark or Anomalous Gluon Interpretation for g1^P(x)?

Hai-Yang Cheng

《Chinese Journal of Physics》 35卷1期 (1997/02) Pp. 25-34

並列摘要

Contrary to what has been often claimed in the literature, we clarify that the hard photon-gluon cross section △σ(subscript hard) ^γG (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 g1^p(x) up to the next-to-leading order of α5 is independent of the factorization convention, e.g., the gauge-invariant or chiral-invariant scheme, chosen in defining △σ(subscript hard) ^γG (x) and the quark spin density. Thereby, it is not pertinent to keep disputing which factorization prescription is correct or which definition for the spin-dependent quark distribution is superior. The hard-gluonic contribution to Γ1^p the first moment of g1^p(x), is purely factorization dependent. Nevertheless, we stress that even though hard gluons do not contribute to Γ1^p 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 Q^2 evolution of parton spin distributions to the next-to-leading order of QCD in the chiral-invariant factorization scheme.