Quark-photon vertex in confining models

We compute the one-loop quark-photon vertex and the quark magnetic moment in three different models with an infrared-modified gluon propagator, namely: the massive (Curci-Ferrari-like) model, the Gribov-Zwanziger model, and the Refined Gribov-Zwanziger model. We show results for the $F_2$ form factor and analyze the role played by the mass parameters associated with the confined gluon in these models. Using the framework of the Constituent Quark Model, we further construct the observable proton magnetic moment including the effects of QCD interactions generated by the different confining models. Our results show that there is no qualitative observable difference stemming from the presence of complex-conjugated poles. On the other hand, quantitative differences between the various confining models can be sizable, so that observable constraints would in principle be possible, provided one has sufficient information about the constituent quark mass and the QCD running coupling.