Quark-gluon interaction in the infrared region of QCD and chromomagnetic moments of quarks

An approximate equation for the quark-gluon vertex in the infrared region of QCD is considered within the framework of the hypothesis of incomplete color confinement. It is shown that for the existence of solutions with quasifree infrared asymptotic forms of the vertex and quark propagator it is necessary to have a condition which fixes the anomalous chromomagnetic moment 2kappa-cur of the quark and which, in the approximation considered, leads to the unique value kappa-cur = 1. The condition for applicability of the approximation imposes a lower bound on the masses of the quarks for which the approximation is valid. The gauge independence of the result is demonstrated by a calculation in the covariant gauge and in the axial gauge. The value obtained for kappa-cur is compared with the results of nonrelativistic potential models for heavy quarkonium