Search for Flavor-Changing Neutral-Current Charm Decays

TL;DR

This paper reports a search for rare charm quark decays involving flavor-changing neutral currents using BABAR data, setting new upper limits on their branching fractions and improving upon previous results.

Contribution

The study provides the first comprehensive search for FCNC charm decays across multiple modes with improved sensitivity and more stringent upper limits.

Findings

Set 90% CL upper limits between 4 and 40×10⁻⁶ on branching fractions.

Achieved significant improvements over previous experimental limits.

Analyzed multiple decay modes including D⁺, D_s⁺, and Λ_c⁺ decays.

Abstract

We search for rare FCNC charm decays of the form $X_c^+\to h^+\llp$, where $X_c^+$ is a charm hadron, $h$ is a pion, kaon or proton, and $\ell^{(}{'}^{)}$ is an electron or a muon. In the pion and kaon modes, we study both $D^+$ and $D_s^+$ decays, while in the proton modes we study $\Lambda_c^+$ decays. Based on a data sample of 288${fb}^{-1}$ of $e^+e^-$ collisions collected by BABAR, we set preliminary 90% confidence level limits between 4 to 40$\times10^{-6}$ for the branching fractions of the different decay modes. For most decay modes, our analysis provides a significant improvement over previous results.