Pionic Parton Distributions Revisited

Abstract

Using constituent quark model constraints we calculate the gluon and sea-quark content of pions solely in terms of their valence density (fixed by \pi N Drell-Yan data) and the known sea and gluon distributions of the nucleon, using the most recent updated valence-like input parton densities of the nucleon. The resulting small-x dynamical QCD predictions for g^{\pi}(x,Q^2) and \bar{q}^{\pi}(x,Q^2) are unique and parameter free. Simple analytic parametrizations of the resulting parton distributions of the pion are presented in LO and NLO. These results and parametrizations will be important, among other things, for updated formulations of the parton distributions of real and virtual photons.