Search for the lepton flavor violating decay J/ψ → eμ

Authors：Ablikim, M.; Achasov, M. N.; Adlarson, P.; Albrecht, M.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai, X. H.; Bai, Y.; Bakina, O.; Ferroli, R. Baldini; Balossino, I; Ban, Y.; Batozskaya, V; Becker, D.; Begzsuren, K.; Berger, N.; Bertani, M.; Bettoni, D.; Bianchi, F.; Bloms, J.; Bortone, A.; Boyko, I; Briere, R. A.; Brueggemann, A.; Cai, H.; Cai, X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.; Chang, W. L.; Chelkov, G.; Chen, C.; Chen, Chao; Chen, G.; Chen, H. S.

Source：Science China: Physics, Mechanics and Astronomy , 2023, 66(2): 221011.

DOI：10.1007/s11433-022-1995-0

• BESIII
• e(+)e(-) experiments
• charmonium
• lepton flavor violating decay

We present a search for the lepton flavor violating decay J/psi -> e(+/-)mu(-/+) using 8.998 x 10(9)J/psi events collected with the BESIII detector at the BEPCII e(+)e(-) storage ring. No excess of signal above background is observed; we therefore set an upper limit on the branching fraction of B(J/psi -> e(+/-)mu(-/+)) < 4.5 x 10(-9) at the 90% confidence level. Improving the previous best result by a factor of more than 30, this measurement places the most stringent limit to date on lepton flavor violation in the heavy quarkonium sector.