Search for Rare Charm Meson Decays at FNAL E791

TL;DR

This study conducted a comprehensive search for rare charm meson decays involving flavor-changing neutral currents and lepton violations, setting new upper limits on their occurrence due to no observed signals.

Contribution

It provides the first extensive search for multiple rare decay channels of charm mesons, improving existing upper limits and reporting new decay modes.

Findings

No evidence of rare decays was observed.

Established 90% confidence level upper limits on branching fractions.

Reported 26 previously unreported decay channels.

Abstract

We report the results of a blind search for flavor-changing neutral current (FCNC), lepton-flavor violating, and lepton-number violating decays of D+, Ds+, and D0 mesons (and their antiparticles) into 2-, 3-, and 4-body states including a lepton pair. Such decays may involve Flavor-Changing Neutral Currents, Leptoquarks, Horizontal Gauge Bosons, or Majorana Neutrinos. No evidence for any of these decays is found. Therefore, we present 90% confidence level branching fraction upper limits, typically at the 0.0001 level. A total of 51 decay channels have been examined; 26 have not been previously reported and 18 are significant improvements over previous results.