On the Lorentz nature of confinement in heavy—light quarkonia

Abstract

The Lorentz nature of the effective interquark interaction in a heavy—light quarkonium is studied using the vacuum correlators method and the generalized Nambu—Jona-Lasinio potential quark model. An effective scalar interaction is demonstrated to appear self-consistently owing to chiral-symmetry breaking and to dominate for low-lying states in the bound-state spectrum. The relation between such an effective interquark interaction and the QCD string approach is discussed. On the contrary, the upper part of this spectrum is found to be governed by the spatial Lorentz vector interaction which leads to a degeneracy for the states with opposite parity—the so-called restoration of chiral symmetry for excited hadrons.