Spurless Method of Calculating the Amplitudes of Reactions Involving Massless Fermions

A new method of calculating the amplitudes of processes involving massless fermions with a spin of 1/2 is suggested in the present paper. The method is based on the use of the isotropic tetrad in Minkowski space and the basic spinors related to it. As an illustration, the amplitudes of the electron-positron annihilation into a fermion pair and the collisions of two -quanta and their transformation into an electron-positron pair are obtained.