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Polarized parton distributions and structure functions
of the nucleon are analyzed in the improved valon model. The valon
representation provides a basis between hadrons and quarks, in
terms of which the bound-state and scattering properties of
hadrons can be united and described. Polarized valon distributions
are defined to have an important role in describing the spin
dependence of parton distribution in leading order and
next-to-leading order approximation. In polarized case,
convolution integral is derived in frame work of valon model.
Polarized valon distribution in a proton and polarized parton
distributions inside the valon are necessary to obtain polarized
parton distributions in a proton. Bernstein polynomial averages
are used to get unknown parameters of polarized valon
distributions by fitting to available experimental data. The
predictions for NLO calculations of polarized parton distributions
and proton structure function have been compared with LO
approximation . It is shown that the results of the calculations
for proton structure function, $xg_1^p$ , and the first moment of
proton, $\Gamma _{1}^p$, are in good agreement with experimental
data for some value of $Q^{2}$. Finally the spin contribution of
valons and proton are calculated.
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