Lava flowing over pQCD: gamma* gamma -> pi^0 

Anatoly Radyushkin
JLab/ODU

A scenario is investigated in which the leading-twist pion distribution 
amplitude phi_pi (x) is approximated by the pion decay constant f_pi 
for all essential values of the light-cone fraction x.

A model for the light-front wave function Psi(x,k_perp) is proposed that 
produces such a distribution amplitude and has a rapidly decreasing 
(exponential for definiteness) dependence on the light-front energy 
combination k_perp^2/x(1-x).

It is shown that this model easily reproduces the fit of recent 
large-Q^2 BaBar data on the photon-pion transition form factor. Some 
aspects of scenario with flat pion distribution amplitude are discussed.