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.