Positronium Decay into a Photon and Neutrinos

TL;DR

This paper calculates the decay rates and spectra of positronium decaying into a photon and neutrinos, revealing new insights into spin state access and the influence of binding effects on the spectra.

Contribution

It demonstrates that both positronium spin states can decay into a photon and neutrinos, correcting previous assumptions, and links the soft photon spectrum to the Stark effect.

Findings

Both spin states can decay into photon and neutrinos.

Spectral tails are sensitive to binding effects and match Low's theorem.

Connection established between soft photon spectrum and Stark effect.

Abstract

We determine the rates and energy and angular distributions of the positronium decays into a photon and a neutrino-antineutrino pair, Ps-->gamma+nu+anti-nu. We find that both positronium spin states have access to this decay channel, contrary to a previously published result. The low-energy tails of the spectra are shown to be sensitive to the binding effects and agree with Low's theorem. Additionally, we find a connection between the behaviour of the soft photon spectrum in both o-Ps-->gamma+nu+anti-nu and o-Ps-->3gamma decays, and the Stark effect.