We consider the decay of positronium to a neutrino-antineutrino accompanied by a single photon. Since the neutrino pair go undetected, this appears as a single photon decay of positronium. These decay channel are mediated through the exchange of the massive $W$ and $Z$ vector bosons of the electroweak interaction. After summing over the various neutrino channels, the standard model calculation yields the rate for such a single photon decay process of $\Gamma_{ Ps \rightarrow \gamma}$ = 1.72 $\times 10^{ -19}$ s$^{ -1}$.
Categories: physics.atom-ph hep-ph physics.chem-ph quant-ph