Hadronic unquenching effects in the quark propagator

Abstract

We investigate hadronic unquenching effects in light quarks and mesons. Within the nonperturbative continuum framework of Schwinger-Dyson and Bethe-Salpeter equations we quantify the strength of the back reaction of the pion onto the quark-gluon interaction. To this end we add a Yang-Mills part of the interaction such that unquenched lattice results for various current quark masses are reproduced. We find considerable effects in the quark mass function at low momenta as well as for the chiral condensate. The quark wave function is less affected. The Gell-Mann-Oakes-Renner relation is valid to good accuracy up to pion masses of 400--500 MeV. As a by-product of our investigation we verify the Coleman theorem, that chiral symmetry cannot be broken spontaneously when QCD is reduced to $1+1$ dimensions.