Measurement of the Bₚ⁰ →μ⁺μ⁻ decay properties and search for the B⁰ → μ⁺μ⁻ decay in proton-proton collisions at √s = 13TeV

Measurements are presented of the B _s ⁰→μ ⁺μ ⁻ branching fraction and effective lifetime, as well as results of a search for the B ⁰→μ ⁺μ ⁻ decay in proton-proton collisions at s=13TeV at the LHC. The analysis is based on data collected with the CMS detector in 2016–2018 corresponding to an integrated luminosity of 140fb ⁻¹. The branching fraction of the B _s ⁰→μ ⁺μ ⁻ decay and the effective B _s ⁰ meson lifetime are the most precise single measurements to date. No evidence for the B ⁰→μ ⁺μ ⁻ decay has been found. All results are found to be consistent with the standard model predictions and previous measurements.