Observation of J / ψ decays to e + e − e + e − and e + e − μ + μ −

Using a data sample of 4.481×108 ψ(3686) events collected with the BESIII detector, we report the first observation of the four-lepton-decays J/ψ→e+e-e+e- and J/ψ→e+e-μ+μ- utilizing the process ψ(3686)→π+π-J/ψ. The branching fractions are determined to be [5.48±0.31(stat)±0.45(syst)]×10-5 and [3.53±0.22(stat)±0.13(syst)]×10-5, respectively. The results are consistent with theoretical predictions. No significant signal is observed for J/ψ→μ+μ-μ+μ-, and an upper limit on the branching fraction is set at 1.6×10-6 at the 90% confidence level. A CP asymmetry observable is constructed for the first two channels, which is measured to be (-0.012±0.054±0.010) and (0.062±0.059±0.006), respectively. No evidence for CP violation is observed in this process. © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.