Observation of J/ψ→3γ
We report the first observation of the decay J/ψ→ 3y. The signal has a statistical significance of 6σ and corresponds to a branching fraction of 'B(J/ψ→ 3y) = (1.2 ± 0.3 ± 0.2) X 10 -5 , in which the errors are statistical and systematic, respectively. The measurement uses ψ(2S) →π + π - J/ψ events acquired with the CLEO-c detector operating at the CESR e + e - collider.