Test of Lepton Flavor Universality with 𝐵⁰_𝑠 →𝜙⁢ℓ⁺⁢ℓ⁻ Decays

Lepton flavor universality in rare 𝑏 →𝑠 transitions is tested for the first time using 𝐵⁰_𝑠 meson decays. The measurements are performed using 𝑝⁢𝑝 collision data collected by the LHCb experiment between 2011 and 2018, corresponding to a total integrated luminosity of 9  fb⁻¹. Branching fraction ratios between the 𝐵⁰_𝑠→𝜙⁢𝑒⁺⁢𝑒⁻ and 𝐵⁰_𝑠 →𝜙⁢𝜇⁺⁢𝜇⁻ decays are measured in three regions of dilepton mass squared, 𝑞², with 0.1<𝑞²<1.1, 1.1 <𝑞² <6.0, and 15<𝑞²<19  GeV²/𝑐⁴. The results agree with the standard model expectation of lepton flavor universality.