QUARK-GLUON VERTEX AND STRUCTURE OF MESONS AND DIQUARKS

Two quark propagators with different analytic structure are employed i n Bethe-Salpeter type equations for the pion and scalar diquark form f actors. One of the quark propagators has been calculated with the incl usion of a trivial (bare) quark-gluon vertex and, as a consequence, co ntains a complex conjugate pair of logarithmic branch points. The othe r quark propagator is obtained using a non-trivial (dressed) vertex an satz and is entire, with an essential singularity at infinity. The eff ects of these different quark propagators on the BSE solutions are com pared.