Test of Lepton Flavor Universality with Bs0 →φℓ+ℓ- Decays

Abstract

Lepton flavor universality in rare b → s transitions is tested for the first time using B0 s meson decays. The measurements are performed using pp 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 B0s → ϕeþe− and B0s → ϕμþμ− 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.