Quark flavor effects on gluon and ghost propagators

We compute the full nonperturbative ghost and gluon two-point Green functions by using gauge field configurations with N f=2 and N f=2+1+1 twisted-mass quark flavors. We use simulations with several different light quark masses, heavy quark masses close to that of the strange and charm quarks, and the lightest pseudoscalar masses ranging from 270 to 510 [MeV]. Quark flavor effects on both the gluon and the ghost propagators are then investigated in a wide range of momenta, bridging the deep infrared and intermediate momenta domain of QCD interactions in the presence of dynamical quarks. The ghost-gluon vertex is also indirectly probed through a consistency requirement among the lattice data for the gluon and ghost propagators and the ghost propagator Schwinger-Dyson equation. The effective full QCD coupling is finally constructed, and its dependence on the presence of dynamical fermions scrutinized. © 2012 American Physical Society.