Pion distribution amplitude and form-factors: Improved Gaussian model of QCD vacuum
Abstract
Description
We describe the present status of the pion distribution amplitude (DA) as it originated from several sources: (i) a nonperturbative approach, based on QCD sum rules with nonlocal condensates, (ii) an O(α_s) QCD analysis of the CLEO data on F^{γγ^*π}(Q^2) with asymptotic and renormalon models for higher twists, and (iii) recent high-precision lattice QCD calculations of the second moment of the pion DA. Then we show the comparison of the results for the pion electromagnetic form factor, obtained in analytic perturbation theory, with JLab data on F_π(Q^2). After that we introduce the improved model for nonlocal condensates in QCD and show its consequences for the pion DA and γγ^*\toπtransition form factor. In order to facilitate possible applications of BMS and improved ``bunches'' we suggest approximate analytic descriptions of their boundaries.
10 pages, 8 figures, invited talk at the International Conference on New Trends in High-Energy Physics, Yalta, Crimea, Ukraine, September 16--23, 2006
10 pages, 8 figures, invited talk at the International Conference on New Trends in High-Energy Physics, Yalta, Crimea, Ukraine, September 16--23, 2006