On the Pion Distribution Amplitude Shape

Understand

We argue that the recent BaBar data on $\gamma \to \pi$ e.m.

• transition form factor at large photon virtuality supports the idea that pion distribution amplitude (DA) is close to unity with $\phi_\pi^\prime(0)/6\gg 1$ at a normalization point of $\mu=0.6\div 0.8$ GeV.
• Such pion DA can be obtained in the effective chiral quark model.
• The possible flat shape of the pion DA implies that the standard expansion of the DA in Gegenbauer polynomials can be divergent.