Calculation of Masses Spectrum and Leptonic Widths of Mesons in the Relativistic Quasipotential Approach

Three-dimensional relativistic two-particle equation in the relativistic configurational representation, obtained within the framework of completely covariant quasipotential approach in Hamiltonian formulation of the quantum field theory is used to describe the masses spectrum and leptonic decay widths of mesons. This quasipotential equation for the case of two particles of arbitrary masses is solved by the WKB approximation. A modified relativistic WKB quantization condition and the expression for the leptonic decay widths of mesons for the singular confining Coulomb-like quasipotential are obtained.