A Model for Dipole Electromagnetic Form Factors

A model of the electromagnetic form factor of the scalar n meson is discussed in which the n meson is a bound state of scalar nucleon-antinucleon system. Starting from an exact integral representation of the form factor, which is well defined in a space-like region of the momentum transfer squared, q2, an analytic continuation of the representation is performed under some plausible assumptions on dynamics and a simple pole definition of a resonance in the n-N scattering amplitude. It is shown that the singularities of the form factor corresponding to resonances turn out to be dipoles and not simple poles contrary to the widely held belief. A generalization to the other hadron cases is discussed in the quark model scheme.