The required <QED Feynman rules> are the electron-photon vertex $-ie\gamma^\mu$, the internal electron propagator
$$
\frac{i(\not k+m)}{k^2-m^2+i\epsilon},
$$
the external spinors $u(p,s)$ and $\bar u(p',s')$, and photon factors $\epsilon_{\rm in}^\nu$ and $\epsilon_{\rm out}^{*\mu}$. Momentum conservation is imposed at both vertices.

Solution

Past exam of the mathematics course of the University of Cambridge / 2019 / iii / Paper 301 / 3 / iv / a / Solution

 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2019/iii/paper-301/3/iv/a/solution