"The puzzles around the pion-photon transition form factor"

by Prof. N. G. Stefanis (Ruhr-Universität Bochum)

Monday 28 Jan 2013, 14:15 → 15:45 Europe/Berlin

3344 (TUM - Physics Department - Garching)

We discuss the pion-photon transition form factor with the help of lightcone sum rules within QCD. The calculation includes NLO radiative corrections and the twist-four term, as well as two- loop evolution. The main NNLO perturbative contribution is taken into account together with the twist-six term in the form of theoretical uncertainties. The pion distribution amplitude is extracted from QCD sum rules using nonlocal condensates. Comparison with the available experimental data shows that the scaling behavior of the form factor at higher momentum | predicted by QCD collinear factorization|is supported by the Belle data (2012) while the BaBar data (2009) indicate above 10 GeV2 an auxetic behavior that is incompatible with the standard QCD scheme. We argue that this antithetic data trend is arti¯cial and explain why the Belle data are the better option.