Lattice simulations of Yang-Mills theories and QCD in the Landau gauge have
demonstrated that the gluon propagator saturates at vanishing momentum. This can
be modeled by a massive deformation of the corresponding Faddeev-Popov
Lagrangian known as the Curci-Ferrari model. The latter does not modify the known
ultraviolet regime of the theory and provides a successful perturbative description of
essential aspects of the non-Abelian dynamics in the infrared regime, where, in