Search for the rare semi-leptonic decay $J/\ddot{I}ˆ\to D^{-}{e}^{+}\hat{I}{½}_e+c.c.$

Abstract

Using $10.1\times 10^9$ $J/\ddot{I}ˆ$ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $\sqrt{s}=3.097\mathrm{GeV}$ and collected with the BESIII detector, we present a search for the rare semi-leptonic decay $J/\ddot{I}ˆ\to D^{-}{e}^{+}\hat{I}{½}_e+c.c.$. No excess of signal above background is observed, and an upper limit on the branching fraction $\mathcal{B}(J/\ddot{I}ˆ\to D^{-}{e}^{+}\hat{I}{½}_e+c.c.)<7.1\times 10^{-8}$ is obtained at $90\%$ confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.