THE BRANCHING FRACTION AND EFFECTIVE LIFETIME OF B 0 (s) → µ + µ − AT LHCb WITH RUN 1 AND RUN 2 DATA

After Run 1 of the LHC, global fits to b → sss observables show a deviation from the Standard Model (SM) with a significance of ∼ 4 standard devations. An example of a b → sss process is the decay of a B 0 s meson into two muons (B 0 s → µ + µ −). The latest analysis of B 0 (s) → µ + µ − decays by LHCb with Run 1 and Run 2 data is presented. The B 0 s → µ + µ − decay is observed for the first time by a single experiment. In addition, the first measurement of the B 0 s → µ + µ − effective lifetime is performed. No significant excess of B 0 → µ + µ − decays is observed. All results are consistent with the SM and constrain New Physics in b → sss processes.