QCD-based pion distribution amplitudes confronting experimental data

We use QCD sum rules with non-local condensates to recalculate more accurat ely the moments and their confidence intervals of the twist-2 pion distribu tion amplitude including radiative corrections. We are thus able to constru ct an admissible set of pion distribution amplitudes which define a reliabi lity region in the a(2), a(4) plane of the Gegenbauer polynomial expansion coefficients. We emphasize that models like that of Chernyak and Zhitnitsky , as well as the asymptotic solution, are excluded from this set. We show t hat the determined a(2), a(4) region strongly overlaps with that extracted from the CLEO data by Schmedding and Yakovlev and that this region is also not far from the results of the first direct measurement of the pion valenc e quark momentum distribution by the Fermilab E791 Collaboration. Compariso ns with recent lattice calculations and instanton-based models are briefly discussed. (C) 2001 Published by Elsevier Science B.V.