  We address the question of the Lorentz nature of the effective interquark
interaction in QCD which leads to the formation of the QCD string between
colour charges. In particular, we start from a manifestly vectorial fundamental
interaction mediated by gluons and demonstrate that, as soon as chiral symmetry
is broken spontaneously, the effective interquark interaction acquires a
selfconsistently generated scalar part which is eventually responsible for the
formation of the QCD string. We demonstrate this explicitly for a heavy-light
quarkonium, using the approach of the Schwinger-Dyson-type equation and the
quantum-mechanical Hamiltonian method of the QCD string with quarks at the
ends.

High Energy Physics - Phenomenology