Low-lying pseudoscalar and vector mesons and their dynamics : How to describe radiative reactions with an odd number of pions

In chiral perturbation theory, the leading-order contribution to reactions with pionsin the sector of odd intrinsic parityis defined by the Wess-Zumino-Witten structure. This structure is supplemented by a simple vector-mesonLagrangian where the vector mesonsare described by antisymmetric tensorfields. With the rho-omega- pioncoupling as the only parameter in the sector of odd intrinsic parity, i.e. without additional contact terms, one can achieve a proper description of the single- and double-virtual piontransition form factor and the three- pionproduction in electron-positron collisions.