Differential Cross-Section

[math]-i \mathfrak{M}_{e^-e^-}=-i \left ( \frac{e^2(\mathbf P_A+\mathbf P_C)_{\mu}(\mathbf P_B+\mathbf P_D)^{\mu}}{(\mathbf P_D-\mathbf P_B)^2}- \frac{e^2(\mathbf P_A+\mathbf P_D)_{\mu}(\mathbf P_B+\mathbf P_C)^{\mu}}{(\mathbf P_C-\mathbf P_B)^2} \right )[/math]

[math] \mathfrak{M}_{e^-e^-}= e^2\left ( \frac{\mathbf P_A \mathbf P_B+\mathbf P_C \mathbf P_D+\mathbf P_C \mathbf P_B+\mathbf P_A \mathbf P_D}{(\mathbf P_D-\mathbf P_B)^2}- \frac{\mathbf P_A \mathbf P_B+\mathbf P_D \mathbf P_C+\mathbf P_D \mathbf P_B+\mathbf P_A \mathbf P_C}{(\mathbf P_C-\mathbf P_B)^2} \right )[/math]

[math]\mathfrak{M}_{e^-e^-}=e^2 \left (\frac{u-s}{t}+\frac{t-s}{u} \right )[/math]