Searches for 25 rare and forbidden decays of $D^{+}$ and $D_s^{+}$ mesons

Abstract

A search is performed for rare and forbidden charm decays of the form $D_{(s)}^{+}\to h^{\pm }{\ell }^{+}{\ell }^{(\prime )\mp }$, where $h^{\pm }$ is a pion or kaon and ${\ell }^{{(}^{\prime })\pm }$ is an electron or muon. The measurements are performed using proton-proton collision data, corresponding to an integrated luminosity of $1.6{\text{fb}}^{-1}$, collected by the LHCb experiment in 2016. No evidence is observed for the 25 decay modes that are investigated and $90\%$ confidence level limits on the branching fractions are set between $1.4\times 10^{-8}$ and $6.4\times 10^{-6}$. In most cases, these results represent an improvement on existing limits by one to two orders of magnitude.

All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2020-007.html (LHCb public pages)