Search for Charged Lepton Flavor Violation at BESIII

TL;DR

This paper reports on searches for charged lepton flavor violation in charmonium decays at BESIII, setting new upper limits on branching fractions and constraining new physics models.

Contribution

It presents the first search for CLFV in specific charmonium decays using large datasets, providing the most stringent upper limits to date.

Findings

No significant CLFV signals observed.

Upper limits on branching fractions are set at 10^{-8} level.

Results constrain Wilson coefficients in effective field theory.

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 $\mathcal{B}(J/\psi\to e\tau)<7.5\times10^{-8}$, $\mathcal{B}(J/\psi\to e\mu)<4.5\times10^{-9}$, and $\mathcal{B}(\psi(3686)\to e\mu)<1.4\times10^{-8}$ at 90\% confidence level. These results provide constraints on Wilson coefficients in effective field theory and probe new physics at high energy scales.