ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2014, vol. 89, p. -
Observation of electromagnetic Dalitz decays J /ψ →pe+e-
Based on a sample of (225.3±2.8)×106 J/ψ events collected with the BESIII detector, the electromagnetic Dalitz decays of J/ψ→Pe+e-(P=η′/η/π0) are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays J/ ψ→η′e+e-, J/ψ→ηe+e-, and J/ψ→π0e+e- are observed for the first time. The branching fractions are determined to be B(J/ψ→η′e+e-)=(5.81±0.16±0.31)×10-5, B(J/ψ→ηe+e-)=(1.16±0.07±0.06)×10-5, and B(J/ψ→π0e+e-)=(7.56±1.32±0.50)×10-7, where the first errors are statistical and the second ones systematic. © 2014 American Physical Society.