Test of Lepton Flavor Universality with B^{0}→K^{*0}ℓ^{+}ℓ^{-} Decays at Large Dilepton Invariant Mass

Muon-electron universality is tested in B^{0}→K^{*0}ℓ^{+}ℓ^{-} decays, in the dilepton-invariant-mass region above the ψ(2S) resonance. The analysis uses beauty mesons produced in proton-proton collisions recorded by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9  fb^{-1}. The ratio of branching fractions between the muon and electron channels R_{K^{*0}} is measured to be 1.08_{-0.12}^{+0.14}(stat)±0.07(syst) for a dilepton-invariant-mass squared above 14.0  GeV^{2}/c^{4}, consistent with the standard model prediction. This result represents the most precise measurement of R_{K^{*0}} in this region and the first such measurement performed at a hadron collider.