Searches for rare or forbidden semileptonic charm decays

Abstract

We present searches for rare or forbidden charm decays of the form X + c → h ± ℓ ∓ ℓ ( ' ) + , where X + c is a charm hadron ( D + , D + s , or Λ + c ), h ± is a pion, kaon, or proton, and ℓ ( ' ) ± is an electron or muon. The analysis is based on 384 fb − 1 of e + e − annihilation data collected at or close to the Υ ( 4 S ) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the 35 decay modes that are investigated. We establish 90% confidence-level upper limits on the branching fractions between 1 × 10 − 6 and 44 × 10 − 6 depending on the channel. In most cases, these results represent either the first limits or significant improvements on existing limits for the decay modes studied.