Quark distribution Functions
Both models, pQCD and a hyperfine perturbed constituent quark model(CQD), show that as the scaling variableThe inclusive double polarization asymmetries can be written in terms of polarized and unpolarized valence quark distributions,
The semi-inclusive pion electro-production asymmetries can be written in terms of the valence quark distributions
where is the measured difference of the yield from oppositely charged pions.
The semi - inclusive asymmetry can be expressed in the following way
The last equation can be expressed as