DYNAMICAL REGIMES OF THE QCD STRING WITH QUARKS

The effective action of the quark-antiquark system at large distances is derived from QCD, implementing the minimal area law of the Wilson l oop. The system is quantized by the path integral method and the quant um Hamiltonian is obtained. two dynamical regimes are found: at large orbital excitations (I much greater than 1) the system behaves as a st ring leading to linear Regge trajectories with a slope 1/2pisigma, whi le at small l one obtains a potential-like relativistic or nonrelativi stic regime. The resulting spectra for these two regimes merge very sm oothly and form a simple pattern of nearly straight-line Regge traject ories with a slope very close to (2pisigma)-1.