Search for D⁰ meson decays to π⁺π^-e⁺e^- and K⁺K^-e⁺e^- final states

A search for D⁰ meson decays to the π⁺π^-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 D⁰→π⁺π^-e⁺e^- is observed for the first time when requiring that the two electrons are consistent with coming from the decay of a φ or ρ⁰/ω meson. The corresponding branching fractions are measured relative to the D⁰→K^-π^-[e⁺e^-]_ρ0/ω decay, where the two electrons are consistent with coming from the decay of a ρ⁰ or ω meson. No evidence is found for the D⁰→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 D⁰→π⁺π^-μ⁺μ^- and D⁰→K⁺K^-μ⁺μ^- decays recently measured by LHCb and confirm lepton universality at the current precision.