Search for the lepton flavor violating decay $J/\ddot{I}ˆ\to e\hat{I}¼$

Abstract

We present a search for the lepton flavor violating decay $J/\ddot{I}ˆ\to e^{\pm }\hat{I}{¼}^{\mp }$ using $8.998\times 10^{9}J/\ddot{I}ˆ$ 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 $\mathcal{B}(J/\ddot{I}ˆ\to e^{\pm }\hat{I}{¼}^{\mp })<4.5\times 10^{-9}$ 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.

12 pages, 4 figures