γ*γ → π(η, η′) transition form factors

The surprising results by the BABAR Collaboration on the pi gamma transition form factor require new thoughts about the high-Q(2) dependence of the form factors with virtual photons. We make use of the anomaly sum rule [J. Horejsi and O. Teryaev, Z. Phys. C 65, 691 (1995).] which relates the hadron spectral density to the axial anomaly [S. Adler, Phys. Rev. 177, 2426 (1969); J. S. Bell and R. Jackiw, Nuovo Cimento A 60, 47 (1969).]. We study the quark-hadron duality relation for this sum rule and find out that the increase of the rescaled form factor Q(2)F(pi gamma)(Q(2)) similar to log(Q(2)) suggested by the BABAR data requires the presence of a 1/s-correction term in the relation between the one-loop spectral density and the hadron-continuum spectral density.