Search for Rare and Forbidden Charm Meson Decays at Fermilab E791

We report the results of a blind search for flavor-changing neutral current, lepton-flavor violating, and lepton-number violating decays of D+, D(s)+, and D0 mesons (and their antiparticles) into modes containing muons and electrons. Using data from Fermilab charm hadroproduction experiment E791, we examine the pi l l and K l l decay modes of D+ and D(s)+ and the l+ l- decay modes of D0. No evidence for any of these decays is found. Therefore, we present branching-fraction upper limits at 90% confidence level for the 24 decay modes examined. Eight of these modes have no previously reported limits, and fourteen are reported with significant improvements over previously published results.