We search for the lepton-flavor-violating decay of the $J/\psi$ into an electron and a muon using $(225.3\pm 2.8)\times {10}^{6}J/\psi$ events collected with the BESIII detector at the BEPCII. Four candidate events are found in the signal region, consistent with background expectations. An upper limit on the branching fraction of $\mathcal{B}(J/\psi \to e\mu )<1.6\times {10}^{-7}$ (90% C.L.) is obtained.

• Received 11 April 2013

DOI:https://doi.org/10.1103/PhysRevD.87.112007