Three-photon annihilation

$e^+e^- \to \gamma\gamma\gamma$

Electron-positron annihilation into three photons. For general $e^+e^-$ collisions both spin states contribute. In positronium, C-parity constrains the decay: para-positronium (${}^1S_0$, $C=+1$) decays to 2$\gamma$, ortho-positronium (${}^3S_1$, $C=-1$) decays to 3$\gamma$.

The dominant decay mode of ortho-positronium (${}^3S_1$). Lifetime $\tau \approx 142$ ns, compared to $\tau \approx 125$ ps for para-positronium decaying to two photons.

No diagrams cataloged for this process yet.