Measurements of the branching fraction ratio B(φ → μ⁺μ⁻)/B(φ → e⁺e⁻) with charm meson decays

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A bstract Measurements of the branching fraction ratio B(φ → μ⁺μ⁻)/B(φ → e⁺e⁻) B ϕ → μ + μ − / B ϕ → e + e − with Dₛ⁺→ π⁺φ D s + → π + ϕ and D + → π + ϕ decays, denoted Rφ πˢ R ϕπ s and Rφ πᵈ R ϕπ d , are presented. The analysis is performed using a dataset corresponding to an integrated luminosity of 5 . 4 fb − 1 of pp collision data collected with the LHCb experiment. The branching fractions are normalised with respect to the B + → K + J/ψ (→ e + e − ) and B + → K + J/ψ (→ μ + μ − ) decay modes. The combination of the results yields Rφ π=1.022± 0.012(stat)± 0.048(syst). R ϕπ = 1.022 ± 0.012 stat ± 0.048 syst . The result is compatible with previous measurements of the ϕ → ℓ + ℓ − branching fractions and predictions based on the Standard Model.