Polarized structure of nucleon in the valon representation

We have utilized the concept of valon model to calculate the spin structurefunctions of proton, neutron and deuteron. The valon structure itself isuniversal and arises from the perturbative dressing of the valence quark inQCD. Our results agree rather well with all the relevant experimental data on$g_{1}^{p, n, d}$ and $g_{A}/g_{v}$, and suggests that the sea quarkcontribution to the spin of proton is consistent with zero. It also revealsthat while the total quark contribution to the spin of valon is almost constantat $Q^{2}>=1$ the gluon contribution grows with the increase of $Q^2$ and hencerequiring a sizable negative orbital angular momentum component $L_z$. Thiscomponent along with the singlet and non-singlet parts are calculated in theNext-to-Leading order in QCD. We speculate that gluon contribution to the spincontent of the proton is about 60% for all $Q^2$ values. Finally, we show thatthe size of gluon polarization and hence, $L_{z}$, is sensitive to the initialscale$Q_{0}^{2}$.Comment: 24 pages, 9 Figure