Measurement of η^′→π+^π-e+ ^e- and η^′→π+^π-μ+ ^μ-

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.