Threshold Resummation S-Factor for a System of Two Relativistic Spinor Quarks

A new threshold resummation S-factor in quantum chromodynamics is obtained for a composite system of two relativistic spin-1/2 quarks having identical masses and interacting via a Coulomb-like chromodynamical potential. The pseudoscalar, vector, and pseudovector cases are considered. The present analysis is performed on the basis of the relativistic quasipotential approach in the Hamiltonian formulation of quantum field theory via a transition to the relativistic configuration representation for the case of a composite system formed by two relativistic particles of equal mass.