Upper limits on charm-changing neutral-current interactions

We report on a search for charm-changing neutral-current decays and lepton-family-number–nonconserving decays of charmed hadrons using inclusive and exclusive decays of charmed hadrons into oppositely charged dileptons. We find no evidence for such interactions. The upper limits on the branching ratio for inclusive charm decay to dileptons are B(c→X${\mu }^{+}$ ${\mu }^{\mathrm{-}}$)<1.8×${10}^{\mathrm{-}2}$, B(c→${\mathrm{Xe}}^{+}$ $e^{\mathrm{-}}$)<2.2×${10}^{\mathrm{-}3}$, and B(c→X${\mu }^{\pm }$ $e^{\mp }$)<3.7×${10}^{\mathrm{-}3}$ at 90% confidence level. Upper bounds are also presented for the branching ratios of several exclusive modes.