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Evidence forηc→γγand measurement ofJ/ψ→3γ
Physical Review D
The decay of J/ψ to three photons is studied using ψ(3686)→π^+π^-J/ψ in a sample of 1.0641×10^8 ψ(3686) events collected with the BESIII detector. Evidence of the direct decay of η_c to two photons, η_c→γγ, is reported, and the product branching fraction is determined to be B(J/ψ→γη_c,η_c→γγ)=(4.5±1.2±0.6)×10^-6, where the first error is statistical and the second is systematic. The branching fraction for J/ψ→3γ is measured to be (11.3±1.8±2.0)× 10^-6 with improved precision.doi:10.1103/physrevd.87.032003 fatcat:pgrsd7hjfjcfdox3j3buuady3e