The mass of the nucleon in a chiral quark-diquark model

The mass of the nucleon is studied in a chiral quark-diquark model. Both scalar and axial-vector diquarks are taken into account for the construction of the nucleon state. After the hadronization procedure to obtain an effective meson-baryon Lagrangian, the quark-diquark self-energy is calculated in order to generate the baryon kinetic term as well as the mass of the nucleon. It turns out that the scalar and axial-vector parts of the self-energy are attractive and repulsive respectively for the mass of the nucleon. We investigate the range of parameters that can reproduce the mass of the nucleon. Furthermore, we try the on-shell approximation in which loop integrals containing axial-vector diquarks are simplified. It is shown thath the on-shell approximation is valid for large values of the nucleon mass.