Search for the semi-muonic charmonium decay J/ψ → D−μ+νμ + c.c.

Using (10087 ± 44) × 10⁶J/ψ events collected with the BESIII detector at the BEPCII e⁺e⁻ storage ring at the center-of-mass energy of √{s } = 3.097 GeV, we present a search for the rare semi-muonic charmonium decay J/ψ → D⁻μ⁺ν_μ + c.c.. Since no significant signal is observed, we set an upper limit of the branching fraction to be B (J/ψ → D⁻μ⁺ν_μ + c.c.) < 5.6 × 10⁻⁷ at 90% confidence level. This is the first search for the weak decay of charmonium with a muon in the final state.