Quark-gluon vertex from Nf=2 lattice QCD

We study the quark-gluon vertex in the limit of vanishing gluon momentum using lattice QCD with two flavors of O(a) improved Wilson fermions, for several lattice spacings and quark masses. We find that all three form factors in this kinematics have a significant infrared strength and that both the leading form factor lambda(1), multiplying the tree-level vertex structure, and the scalar, chiral symmetry breaking form factor lambda(3) are significantly enhanced in the infrared compared to the quenched (N-f = 0) case. These enhancements are orders of magnitude larger than predicted by one-loop perturbation theory. We find only a weak dependence on the lattice spacing and quark mass.

Automated summary

The study shows that the quark-gluon vertex has significant infrared strength in the limit of vanishing gluon momentum, with the form factors lambda(1) and lambda(3) being significantly enhanced in the infrared compared to the quenched case. The enhancements are orders of magnitude larger than predicted by one-loop perturbation theory, with only a weak dependence on lattice spacing and quark mass.