Measurement of the decay properties and search for the B → μ Μ Decay in Proton-proton Collisions at

Measurements are presented of the ${\text{B}}_{\text{s}}^{0}\to {\mu }^{+}{\mu }^{-}$ branching fraction and effective lifetime, as well as results of a search for the ${\text{B}}^{0}\to {\mu }^{+}{\mu }^{-}$ decay in proton-proton collisions at $\sqrt{s}=13\phantom{\rule{0.2em}{0ex}}\text{TeV}$ at the LHC. The analysis is based on data collected with the CMS detector in 2016–2018 corresponding to an integrated luminosity of 140$\phantom{\rule{0.2em}{0ex}}{\text{fb}}^{-1}$. The branching fraction of the ${\text{B}}_{\text{s}}^{0}\to {\mu }^{+}{\mu }^{-}$ decay and the effective ${\text{B}}_{\text{s}}^{0}$ meson lifetime are the most precise single measurements to date. No evidence for the ${\text{B}}^{0}\to {\mu }^{+}{\mu }^{-}$ decay has been found. All results are found to be consistent with the standard model predictions and previous measurements.