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

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