ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2013, vol. 87, p. -
Evidence for η<inf>c</inf>→γγ and measurement of J/ψ→3γ
© 2013 American Physical Society. The decay of J/ψ to three photons is studied using ψ(3686) →π<sup>+</sup>π<sup>-</sup>J/ψ in a sample of 1.0641×108 ψ(3686) events collected with the BESIII detector. Evidence of the direct decay of η<inf>c</inf> to two photons, η<inf>c</inf>→γγ , is reported, and the product branching fraction is determined to be B(J/ψ→γη<inf>c</inf>,η<inf>c</inf>→γγ)= (4.5±1.2±0.6)×10<sup>-</sup>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<sup>-</sup>6 with improved precision.