Search for rare and forbidden charm meson decays at Fermilab E791

The authors report the results of a blind search for flavor-changing neutral current, lepton-flavor violating, and lepton-number violating decays of D+, Ds+, and D0 mesons (and their antiparticles) into modes containing muons and electrons. Using data from Fermilab charm hadroproduction experiment E791, they examine the πellell and Kellell decay modes of D+ and Ds+ and the ell+ell- decay modes of D0. No evidence for any of these decays is found. Therefore, they 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