A study of the decay
D0→K−π+μ+μ− is performed using data collected by the LHCb detector in proton–proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of
2.0 fb−1. Decay candidates with muon pairs that have an invariant mass in the range
675–875 MeV/c2 are considered. This region is dominated by the
ρ0 and
ω resonances. The branching fraction in this range is measured to be
This is the first observation of the decay
D0→K−π+μ+μ−. Its branching fraction is consistent with the value expected in the Standard Model.
