Valence quark spin distribution functions

Physical Review D - Particles, Fields, Gravitation and Cosmology

Volumn 59, Issue 3, 1999, Pages

  Isgur, Nathan ^a  

^a THOMAS JEFFERSON NATIONAL ACCELERATOR FACILITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 17044401690     PISSN: 15507998     EISSN: 15502368     Source Type: Journal    
DOI: 10.1103/PhysRevD.59.034013     Document Type: Article

References (46)

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26. In lectures at the 1977 Zakopane Summer School [N. Isgur, Acta Phys. Pol. B 8, 1081 (1977)], I argued that the (Formula presented) splitting suggests that (Formula presented) is broken in such a way that the neutron charge radius and the observation that (Formula presented) as (Formula presented) in deep inelastic scattering might be explained as related effects. This discussion was based on the observation that the spin wave function (7) may be written in the form (Formula presented) and interpreted as an expansion of (Formula presented) in the nonorthogonal basis (Formula presented) in which the (Formula presented) pairs (13) and (23), respectively, form a tightly bound spin zero “core.” While qualitatively correct, as with Refs. 12131415 it is unclear whether the conclusions drawn in this framework about the full valence region survive antisymmetrization.
27. In addition to valence quark models based on the nucleon’s confinement-dominated wave function, there is a proposal by Farrar and Jackson that as (Formula presented) the distribution functions will be dominated by hard perturbative precesses [G. Farrar and D. Jackson, Phys. Rev. Lett. 35, 1416 (1975);
28. for a recent exposition see S. J. Brodsky, M. Burkardt, and I. Schmidt, Nucl. Phys. B441, 197 (1995)]. In that case near (Formula presented) (Formula presented) (Formula presented) (Formula presented) and (Formula presented) where now the parallel distribution function (Formula presented) dominates over the antiparallel distribution function (Formula presented) as (Formula presented) This model thus leads to (Formula presented) as (Formula presented) but still predicts that both (Formula presented) and (Formula presented) as (Formula presented) While (Formula presented) seems to have fallen well below (Formula presented) it could be argued that this discrepancy is due to errors in extracting (Formula presented) from deuterium data. This issue would be worth examining in the light of new high precision data and modern theories of the deuteron’s high momentum structure.
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