Double Dalitz decay
= Double Dalitz decay
{title2=$\pi^0\to\gamma^*\gamma^*\to e^+e^-e^+e^-$}
<Double Dalitz decay> converts both virtual <photons> from a two-photon hadronic transition into charged-lepton pairs. The neutral-<pion> four-electron final state avoids the specific two-lepton <helicity suppression> of $\pi^0\to e^+e^-$, despite its more restricted <phase space>.