Dynamical parton distributions of the proton and small-x physics

The perturbative properties of parton distributions generated radiatively from a valence-like input at some low resolution scale are discussed with the aim of explaining the physical aspects underlying the reliability of the predicted distributions in the small-x region. Aspects of higher-twist (shadowing) effects as well as small-x resummations are discussed. Utilizing recent improved data at x > or ∼ 10-2 and a factorization scheme in which the heavy quarks c,b, .., are not entailed among the intrinsic (massless) parton distributions, we readjust our valence-like input and provide parametrizations of the slightly modified dynamical LO and NLO (MS, DIS) predictions for parton distributions. (orig.)