Pion distribution amplitude -- from theory to data (CELLO, CLEO, E-791, JLab F(pi))

Abstract

In my talk I discuss the theoretical and experimental status of the pion distribution amplitude (DA). I show that the QCD sum rule method with nonlocal condensates (NLC) for the pion DA gives us admissible sets (bunches) of DAs for each value of QCD-vacuum nonlocality parameter λ_q. Comparing these bunches with the new CLEO constraints, obtained in the NLO light-cone sum-rule analysis of γ^*γ\toπ-transition form factor, allows us to fix the value of QCD vacuum nonlocality λ_q^2\simeq0.4 GeV^2. Then I show that the corresponding bunch of pion DAs agrees well with the E791 data on diffractive dijet production and with the JLab F(pi) data on the pion electromagnetic form factor. The latter comparison is made in the framework of analytic perturbation theory with non-power NLO for the pion form factor, where scale-setting ambiguities are strongly reduced already at the NLO level.