in this work.

The structure of this paper is as follows. Sections \[sec:Conventions\]-\[sec:Preliminary\] provide the tools required for the evaluation of the cross sections. The cross sections are derived for all relevant processes in Section \[sec:Derivation\] and are presented in tabular and schematic forms in Section \[sec:Summary\]. Section \[sec:Discrepancies\] provides a discussion of those of the discrepancies in the literature which I am aware of. Section \[sec:Conclusions\] briefly summarises the findings of this paper.

\[sec:Conventions\]Notation and conventions
===========================================

In the present work, all physical variables and observables refer to the ‘centre of momentum’ (CM) frame of reference (unless, of course, they are Lorentz-invariant quantities, in which case there is no need to specify a frame of reference). Only processes with two particles in both the initial and final states are considered (i.e., $2 \to 2$ scattering). Used are the following notations and conventions.

-   The speed of light in vacuum $c$ is equal to $1$.

-   Einstein’s summation convention is used.

-   $I_n$ denotes the $n \times n$ identity matrix.

-   $A^\dagger$ denotes the Hermitian (conjugate transpose) of a square matrix $A$.

-   $g_{\mu \nu}$ denotes the Minkowski metric with signature ‘$+ \, - \, - \, -$’.

-   $\gamma_{\mu}$ 