Evidence for the decay $B^0\to {\mu }^{+}{\mu }^{-}$ and improved measurements of the decay $B_s^0\to {\mu }^{+}{\mu }^{-}$

Abstract

The first single-experiment evidence for the rare decay $B^0\to {\mu }^{+}{\mu }^{-}$ and the world's most precise measurements of the $B_s^0\to {\mu }^{+}{\mu }^{-}$ branching fraction and effective lifetime are reported. The results are obtained using Run 3 proton-proton collision data corresponding to an integrated luminosity of 18 fb${}^{-1}$ recorded with the LHCb Upgrade I detector at a centre-of-mass energy of $13.6$ TeV between 2024 and 2025. Their combination with the Run 1 and Run 2 LHCb results further improves the precision. All measurements are found to be in agreement with the Standard Model expectations.

arXiv commentAll figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lhcb-glance.cern.ch/alcm/public/analysis/full-details/6370/ (LHCb public pages)