Tests for the asymptotic behaviour of the gamma^* --> gamma pi^0 form factor

Abstract

The gamma^* --> gamma pi^0 transition measured at different photon virtualities already provides us with a clean test for the behaviour of the pi^0 gamma^* gamma off-shell axial anomaly at large time-like squared momenta. It also allows reliable predictions for the branching ratio of heavy quarkonium decays into omega pi^0.

Comments: Latex, 7 pages + 1 .ps figure, comments on the Brodsky-Lepage limit and 5 new references added