Based on a sample of 225.3 million J/ψ events accumulated with the BESIII detector at the BEPCII, the decays of η′→π +π-l+l- are studied via J/ψ→γη′. A clear η′ signal is observed in the π+π-e+e - mass spectrum, and the branching fraction is measured to be B(η′→π+π-e +e-)=(2.11±0.12(stat)±0.14(syst)) ×10-3, which is in good agreement with theoretical predictions and the previous measurement, but is determined with much higher precision. No η′ signal is found in the π+π -μ+μ- mass spectrum, and the upper limit is determined to be B(η′→π+π -μ+μ-)<2.9×10-5 at the 90% confidence level.
|Original language||English (US)|
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|State||Published - May 28 2013|
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© 2013 American Physical Society.