The branching ratio (BR) for the rare decay η→π0γγ was measured with the Crystal Ball multiphoton spectrometer. The result, BR(η→π0γγ)=(3.5±0.7stat±0.6syst) ×10-4, is in agreement with calculations of chiral perturbation theory to third order. We have used a sample of 28 million η mesons produced at the BNL Alternating Gradient Synchrotron using the π-p→ηn reaction close to threshold. We detail the intricate extraction of the signal, which has about 1.6 thousand η→π0γγ events, from the overwhelming background of η→3π0 decays and from the π-p→π0π0n reaction.
ASJC Scopus subject areas
- Nuclear and High Energy Physics