Pion Distribution Amplitude and Photon-to-Pion Transition Form Factor in QCD

Abstract

We discuss the status of the pion distribution amplitude (DA) in connection with QCD sum rules and experimental data on the ${\gamma }^{\ast }{\gamma }^{\to }{\pi }^0$ transition form factor. Contents: (a) Pion DA in generalized QCD Sum Rules (SRs); (b) Light Cone Sum Rules (LCSR) analysis of the CLEO data for the ${\gamma }^{\ast }\gamma \to {\pi }^0$ transition form factor; (c) Recent lattice QCD data for the pion DA; (d) BaBar data---a challenge for QCD?

Comments: 6 pages, 3 figures, talk delivered by the first author at the International Meeting "Excited QCD'', January 31--February 5, 2010, Tatranska Lomnica (Slovakia)