The structure of hadronic transition amplitudes h→h′+h″ via quark triangle loops is investigated in terms of hadron quark vertex functions [Formula: see text], using for illustration the case of the ρ→ππ transition. A Bethe-Salpeter model based on the Covariant-Instantaneity-Ansatz (CIA) for its kernel which provides an exact interconnection between the 3D and 4D forms the BS wave function, determines the structure [Formula: see text]. The nonlocality feature inherent in the vertex function causes the imaginary part of gρππ calculated from the loop integral to be generally different from its dispersion relation value which would be obtained from analyticity of gρππ in the ρ-mass. Pending a proper understanding of this nonlocality (associated with confining interactions) only the real part of gρππ is found unambiguous while the imaginary part is model-dependent.

The electromagnetic form factor of the pion is studied using a simple relativistic quark model based on a dynamical picture of the pion as a bound state of the constituent qq-system. * * * One of us (Mamta) would like to thank CSIR for financial support.

We present a relativistic quark model analysis of radiative pion decay using a systematic application of Low’s bremsstrahlung theorem. Our findings agree reasonably with recent definitive experimental results by the Russian group on the structure-dependent components of the πγA and πγV amplitudes, with the latter agreeing remarkably well with the CVC prediction. Finally we analyze between the quark model calculation and the current algebra prediction and establish the equivalence of the two within the limit of a local πqq interaction.