Eur. Phys. J. Plus (2021) 136: 302
https://doi.org/10.1140/epjp/s13360-021-01284-4

Regular Article

Relativistic Coulomb $\mathit{S}$-factor of two spinor particles with arbitrary masses

¹ Gomel State Technical University, 246746, Gomel, Belarus
² Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980, Dubna, Russia
³ International Center for Advanced Studies, Gomel State Technical University, 246746, Gomel, Belarus

^b kaptari@theor.jinr.ru

Received: 28 December 2020
Accepted: 26 February 2021
Published online: 8 March 2021

Abstract

A new resummation of the S-factor of a composite system of two relativistic spin-1/2 particles of arbitrary masses interacting via a Coulomb-like chromodynamical potential is presented. The analysis is performed in the framework of a relativistic quasipotential approach based on the Hamiltonian formulation of the covariant quantum field theory in the relativistic configuration representation. The pseudoscalar, vector, and pseudovector systems are considered, and the behavior of the S-factor near the threshold and in the relativistic limit is investigated in detail. The spin dependence of the S-factors is discussed as well. It is argued that at the threshold the contribution of spins significantly reduces the Sommerfeld effect, while at ultrarelativistic velocities their role diminishes and the S-factor becomes basically the same as for the spinless systems. A connection between the new and previously obtained S-factors for spinless particles of arbitrary masses and for relativistic spinor particles of equal masses is established.