Quantum Statistical Parton Distributions and the Spin Crisis

Quantum statistical distributions for the partons provide a fair descriptionof deep inelastic scattering data at $Q^2 = 3$ and $10 (GeV/c)^2$. The study ofthe polarized structure functions seems to suggest an alternative possiblesolution of the {\it spin crisis} based on the Pauli principle. In this scheme,in fact, the defects of the Gottfried sum rule and Ellis--Jaffe sum rule forproton, result strongly connected. This possibility finds particular evidencefrom the phenomenological observation that the relation $\Delta u = 2 \tilde{F}+ u - d -1$ seems well satisfied by parton distributions.Comment: plain LaTeX, 18 pages + 14 figures, revised version with changes in the text and in some figures, to appear in Progress of Theor. Phys. Vol. 96 (October 1996) No.