Speaker
Description
Charmonium weak decay is allowed in the Standard Model but has never been observed. Using $(10087\pm44)\times{10}^6$ $J/\psi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ storage ring at the center-of-mass energy of $\sqrt s=3.097\ \rm{GeV}$, we present a search for the charmonium rare semi-muonic decay $J/\psi\rightarrow D^-\mu^+\nu_\mu$ and its charge conjugation ($c.c.$) mode. Since no significant signal above the background is observed, we set an upper limit of the branching fraction to be $\rm{BF}(J/\psi\rightarrow D^-\mu^+\nu_\mu+c.c.)<5.6\times{10}^{-7}$ at a confidence level of 90%. This is the first search for the weak decay of charmonium with a muon in the final state and the measurement is compatible with the SM theoretical predictions.
