Searches for Rare and Forbidden Decays of Charm: Recent Results from FNAL

Abstract

We review results on rare and forbidden decays of D^0, D^+, and D^+_s mesons from experiments at FNAL. The decay modes studied have two leptons in the final state and, if observed, would constitute evidence for flavor-changing neutral-current, lepton-flavor-violating, or lepton-number-violating processes. To date, no evidence for these decays has been observed and upper limits are obtained for their branching fractions. These limits can constrain various extensions to the Standard Model. We present new upper limits from FNAL E791 on the branching fractions for more than two dozen three- and four-body decay modes.