Search for the flavor-changing neutral current decay D0→μ0+μ- with the HERA-B detector

Abstract We report on a search for the flavor-changing neutral current decay D 0 → μ + μ − using 50 × 10 6 events recorded with a dimuon trigger in interactions of 920 GeV protons with nuclei by the HERA-B experiment. We find no evidence for such decays and set a 90% confidence level upper limit on the branching fraction B ( D 0 → μ + μ − ) 2.0 × 10 − 6 .