Search for charged lepton flavor violation in $J/\ddot{I}ˆ$ decays at BESIII

Abstract

In the Standard Model, charged lepton flavor violation (CLFV) is heavily suppressed by tiny neutrino mass, while many theoretical models can enhance CLFV effects up to a detectable level. The observation of any CLFV process would be a clear signal of new physics beyond SM. BESIII experiment collected 10 billion $J/\ddot{I}ˆ$ data and searched for CLFV processes $J/\ddot{I}ˆ\to e\ddot{I}„$ and $e\hat{I}¼$. The upper limits at the 90% confidence level are determined to be $\mathcal{B}(J/\ddot{I}ˆ\to e\ddot{I}„)<7.5\times 10^{-8}$ and $\mathcal{B}(J/\ddot{I}ˆ\to e\hat{I}¼)<4.5\times 10^{-9}$, respectively. Improving the previously experimental limits by two orders of magnitudes, the results are the most stringent CLFV searches in the heavy quarkonium system.

6 pages, 2 figures