Quark distribution Functions
Both models, pQCD and a hyperfine perturbed constituent quark model(CQD), show that as the scaling variable
The inclusive double polarization asymmetriesin the valence region, where the scaling variable 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