Search for $D^0$ meson decays to $\ddot{I}{€}^{+}\ddot{I}{€}^{-}{e}^{+}{e}^{-}$ and $K^{+}{K}^{-}{e}^{+}{e}^{-}$ final states

Abstract

A search for $D^0$ meson decays to the $\ddot{I}{€}^{+}\ddot{I}{€}^{-}{e}^{+}{e}^{-}$ and $K^{+}{K}^{-}{e}^{+}{e}^{-}$ final states is reported using a sample of proton-proton collisions collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb${}^{-1}$. The decay $D^0\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}{e}^{+}{e}^{-}$ is observed for the first time when requiring that the two electrons are consistent with coming from the decay of a $\ddot{I}•$ or $\ddot{I}{}^0/\ddot{I}‰$ meson. The corresponding branching fractions are measured relative to the $D^0\to K^{-}\ddot{I}{€}^{-}[e^{+}{e}^{-}{]}_{\ddot{I}{}^0/\ddot{I}‰}$ decay, where the two electrons are consistent with coming from the decay of a $\ddot{I}{}^0$ or $\ddot{I}‰$ meson. No evidence is found for the $D^0\to K^{+}{K}^{-}{e}^{+}{e}^{-}$ decay and world-best limits are set on its branching fraction. The results are compared to, and found to be consistent with, the branching fractions of the $D^0\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ and $D^0\to K^{+}{K}^{-}\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ decays recently measured by LHCb and confirm lepton universality at the current precision.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/1611/ (LHCb public pages)