Measurements are presented of the B0s→μ+μ−branching fraction and effective lifetime, as well as results of a search for the B0→μ+μ−decay in proton-proton collisions at √s=13 TeVat 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 B0s→μ+μ−decay and the effective B0smeson lifetime are the most precise single measurements to date. No evidence for the B0→μ+μ−decay has been found. All results are found to be consistent with the standard model predictions and previous measurements.
