Search for Charged Lepton Flavor Violation at BESIII

Abstract

Charged lepton flavor violation (CLFV) is forbidden in the Standard Model but predicted by many new physics models. We present searches for CLFV in charmonium decays using world-leading datasets collected by the BESIII detector. The processes $J/\psi \to e\tau$, $J/\psi \to e\mu$, and $\psi (3686)\to e\mu$ are investigated using world-leading $J/\psi$ and $\psi (3686)$ dataset collected by BESIII. No significant signals are observed, and upper limits on branching fractions are set at $\mathcal{B}(J/\psi \to e\tau )<7.5\times 10^{-8}$, $\mathcal{B}(J/\psi \to e\mu )<4.5\times 10^{-9}$, and $\mathcal{B}(\psi (3686)\to e\mu )<1.4\times 10^{-8}$ at 90\% confidence level. These results provide constraints on Wilson coefficients in effective field theory and probe new physics at high energy scales.

arXiv commentPresented at the 32nd International Symposium on Lepton Photon Interactions at High Energies Madison, Wisconsin, USA, Augues 25-29, 2025