Search for the charged lepton flavor violating decay $J/\psi \to e\tau $

A search for the charged lepton flavor violating decay $J/\psi \to {e}^{±}{\tau }^{\mp }$ with ${\tau }^{\mp }\to {\pi }^{\mp }{\pi }^{0}{\nu }_{\tau }$ is performed with about $10×{10}^{9}\text{}\text{}J/\psi $ events collected with the BESIII detector at the BEPCII. No significant signal is observed, and an upper limit is set on the branching fraction $B\left(J/\psi \to {e}^{±}{\tau }^{\mp }\right)<7.5×{10}^{-8}$ at the 90% confidence level. This improves the previously published limit by two orders of magnitude.