The asymptotics of the transition form factor γγ* rarrow π0

In this paper the authors present the result of a direct QCD sum rule calculation of the transition form factor γγ* rarrow π0 in the region of moderately large invariant momentum Q2 > 1GeV2 of the virtual photon. In contrast to pQCD, they make no assumptions about the shape of the pion distribution amplitude varphiπ(x). Their results agree with the Brodsky-Lepage proposal that the Q2-dependence of this form factor is given by an interpolation between its Q2=0 value fixed by the axial anomaly and 1/Q2 pQCD behavior for large Q2, with normalization corresponding to the asymptotic form varphipias(x)=6 fπx(1minusx) of the pion distribution amplitude. Their prediction for the from factor Fγ*γ*π0(q12 = 0,q22 = minusQ2) is in good agreement with new CLEO data