Time-like Transition Form Factors of Mesons

Time-like transition form factors are determined via meson decaysinto final states with dileptons. Form factors are evaluated as afunction of the momentum transfer which is identical to the invariantmass of the dileptons. The results provide basic knowledge of thestructure of hadrons and address the validity of vector meson dominance.Transition form factors are of special interest on account of theimpact on the interpretation of the g-2 measurements. Here, light-by-lightscattering is an important factor.The presentations contain three parts: Introduction, Experiments, and Results