Test of lepton flavour universality with Bₛ⁰→ϕℓ⁺ℓ⁻ decays arxiv.org/abs/2410.13748 - Branching fraction ratios between the Bₛ⁰→ϕe⁺e⁻ and Bₛ⁰→ϕμ⁺μ⁻ decays are measured in three regions of dilepton mass squared and agree with the Standard Model expectation of lepton flavour universality.

We inadvertently wrote an earlier version of this post suppressing the "ϕ". Would have been nice.