Measurement of the B0s → μμ effective lifetime with the ATLAS detector

This paper reports the first ATLAS measurement of the Bs0→ μμ effective lifetime. The measurement is based on the data collected in 2015–2016, amounting to 26.3 fb−1 of 13 TeV LHC proton-proton collisions. The proper decay-time distribution of 58 ± 13 background-subtracted signal candidates is fit with simulated signal templates parameterised as a function of the Bs0 effective lifetime, with statistical uncertainties extracted through a Neyman construction. The resulting effective measurement of the Bs0→ μμ lifetime is 0.99−0.07+0.42 (stat.) ± 0.17 (syst.) ps and it is found to be consistent with the Standard Model. © The Author(s) 2023.