QCD sum rule calculation of gamma gamma*->pi(0) transition form factor

We develop a QCD sum rule analysis of the form factor F-gamma*gamma*pi?o (q(2), Q(2)) in the region where virtuality of one of the spacelike photons is small q(2) much less than 1 Ge(V)2 while another is large: Q(2) greater than or similar to 1 GeV2. We construct the operator product expansion suitable for this kinematic situation and obtain a QCD sum rule for F-gamma*gamma*pi?o(0, Q(2)) = F-gamma gamma*pi?o(Q(2)). Our results confirm expectation that the momentum transfer dependence of the leading-order contribution to F-gamma gamma*pi?o(Q(2)) is close to interpolation between its Q(2) = 0 value fixed by the axial anomaly and 1/Q(2) pQCD behaviour for large Q(2). Our approach, in contrast to pQCD, does not require explicit assumptions about the shape of the pion distribution amplitude phi(pi)(x). The absolute value of the 1/Q(2) term obtained in this paper favours phi(pi)(x) close to the asymptotic form phi(pi)(as)(x) = 6f(pi)(1 - x).