Non-perturbative propagators and running coupling in the conformal window of QCD

Using the Dyson-Schwinger approach we investigate QCD with a relatively large number of quark flavours in the chiral limit. A self-consistent treatment of the corresponding propagator equations enables us to study unquenching effects directly via the quark loop diagram in the gluon equation. Above the critical number of fermion flavours the non-perturbative running coupling develops a plateau over a wide momentum range. Correspondingly, the propagators follow a power law behaviour in this momentum range indicating conformal behaviour. Our value $N_f^{crit}\approx 4.5$ is strongly sensitive to the details of the quark-gluon vertex calling for a more detailed investigation of this object.