Search for the rare semi-leptonic decay J/ψ → D−e+νe + c.c.

A bstract Using 10 . 1 × 9 J/ψ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $$ \sqrt{s} s = 3 097 GeV and collected with BESIII detector, we present search for rare semi-leptonic decay → D − e + ν c.c. No excess of signal above background is observed, an upper limit on branching fraction ℬ( J / ψ c .) < 7.1 −8 obtained 90% confidence level. This improvement more than two orders magnitude over previous best limit.