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Dynamical parton densities, generated radiatively from valence-like inputs at some low resolution scale, are confronted with recent small-x data on deep inelastic and other hard scattering processes. It is shown that within theoretical uncertainties our previous (1994) dynamical/radiative parton distributions are compatible with most recent data and still applicable within the restricted accuracy margins of the presently available next-to-leading order calculations. Due to recent high precision measurements we also present an updated, more accurate, version of our (valence-like) dynamical input distributions. Furthermore, our perturbatively stable parameter-free dynamical predictions are extended to the extremely small-x region, 10 −8 < ∼ x < ∼ 10 −5 , relevant to questions concerning ultra-high-energy cosmic ray and neutrino astronomy.

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Polarized deep inelastic scattering ͑DIS͒ data are analyzed in leading and next-to-leading order of QCD within the common ''standard'' scenario of polarized parton distributions with a flavor-symmetric light sea ͑antiquark͒ distribution ␦q , and a completely SU͑3͒ f broken ''valence'' scenario with totally flavorasymmetric light sea densities (␦ū ␦d ␦s). The latter flavor-broken light sea distributions are modeled with the help of a Pauli-blocking ansatz at the low radiative or dynamical input scales of LO͑NLO͒ 2 ϭ0.26 (0.40) GeV 2 which complies with predictions of the chiral quark-soliton model and expectations based on the statistical parton model as well as with the corresponding, well established, flavor-broken unpolarized sea (d Ͼū ). Present semi-inclusive DIS data cannot yet uniquely discriminate between those two flavorsymmetric and flavor-broken polarized light sea scenarios.

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