Štúdium vlastností B0d mezónu na experimente ATLAS

Biroš, Marek

Title: Studies of B0 d meson properties with the ATLAS experiment Author: Marek Biroš Institute: Institute of Particle and Nuclear Physics Supervisor: doc. RNDr. Pavel Řezníček Ph.D., Institute of Particle and Nuclear Physics Abstract: A precision measurement of the effective lifetime of the B0 d meson τB0 d with the ATLAS detector is presented. The decay channel B0 d → J/ψK∗0 is used with a dataset corresponding to an integrated luminosity of 140.1 fb−1 of proton-proton collisions at √ s = 13 TeV, recorded during Run 2 of the LHC. A two-dimensional unbinned maximum likelihood fit to the invariant mass and proper decay time distributions is employed to separate signal and background components and to extract the effective lifetime of the B0 d meson. The analysis incorporates advanced statistical techniques, including per-event proper decay time uncertainties and the sPlot technique. The average decay width Γd is also extracted using external inputs. Furthermore, the ratio Γd/Γs is determined as well combining with the previous ATLAS measurement of Γs. The measured values are: τB0 d = 1.5053 ± 0.0012 (stat) ± 0.0035 (syst) ps, Γd = 0.6639 ± 0.0005 (stat.) ± 0.0016 (syst.) ± 0.0038 (ext.) ps−1 , Γd/Γs = 0.9905 ± 0.0022 (stat.) ± 0.0036 (syst.) ± 0.0057 (ext.). These results are consistent with Standard Model...

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