On Threshold Resummation S-Factor for a System of Two Relativistic Spinor Particles with Arbitrary Masses

We present a new threshold resummation S-factor obtained for a composite system of two relativistic spin 1/2 particles of arbitrary masses interacting via a Coulomb-like chromodynamical potential. The analysis is performed in the framework of a relativistic quasipotential approach in the Hamiltonian formulation of the quantum field theory in the relativistic configuration representation. The pseudoscalar, vector, and pseudovector systems are considered. The difference in the behavior of the S-factor for these cases is discussed. A connection between the new and the previously obtained S-factors for spinless particles of arbitrary masses and relativistic spinor particles of equal masses is established.