PHENOMENOLOGICAL APPROACH TO UNPOLARIZED AND POLARIZED PARTON DISTRIBUTIONS AND EXPERIMENTAL TESTS

We recall our recent description of quark parton densities of the prot on at Q(2) = 4 GeV2 in terms of Fermi-Dirac distributions parametrized with very few free parameters. We have also proposed some simple assu mptions to relate unpolarized and polarized quark parton densities whi ch lead to a fair description of the spin-dependent structure function s xg(1)(p)(x, Q(2)) and xg(1)(n)(x, Q(2)) at low Q(2). We will show th e predictions we obtain after a straightfonvard DGLAP Q(2) evolution a nd comparison in a much broader x and Q(2) range, with several recent and accurate deep-inelastic scattering data. In particular, we will se e that we get an excellent agreement with the sharp rise of F-2(ep)(x, Q(2)) for small x, recently observed at HERA. Finally, we give severa l predictions for lepton pair and gauge boson production in pp and pn collisions at high energies which will be tested in the future at RHIC .