A Covariant Method for Calculating Amplitudes of Processes Involving Polarized Spin 1/2 Particles. Calculation of the Interference Terms in their Cross Sections

A covariant method is proposed for calculating the amplitudes of processes involving polarized spin 1/2 particles. It is suitable for calculating the interference terms in the cross sections of such processes. As an illustration, expressions are given for the amplitudes of electron-electron scattering in the lowest order of perturbation theory and expressions for the electron current in the case of emission of two bremsstrahlung photons in the ultrarelativistic limit.