Study of two-photon decays of pseudoscalar mesons via J/ψ radiative decays

Abstract

Using a sample of 4.48 × 10 8 ψ ( 3686 ) events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons π 0 , η , η ′ , η ( 1405 ) , η ( 1475 ) , η ( 1760 ) , and X ( 1835 ) in J / ψ radiative decays using ψ ( 3686 ) → π + π − J / ψ events. The π 0 , η , and η ′ mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be B ( J / ψ → γ π 0 → 3 γ ) = ( 3.57 ± 0.12 ± 0.16 ) × 10 − 5 , B ( J / ψ → γ η → 3 γ ) = ( 4.42 ± 0.04 ± 0.18 ) × 10 − 4 , and B ( J / ψ → γ η ′ → 3 γ ) = ( 1.26 ± 0.02 ± 0.05 ) × 10 − 4 , where the first error is statistical and the second is systematic. No clear signal for η ( 1405 ) , η ( 1475 ) , η ( 1760 ) or X ( 1835 ) is observed in the two-photon mass spectra, and upper limits at the 90% confidence level on the product branching fractions are obtained.