Thesis defense of Marc Quentin Führing

In this thesis, two decay-time-dependent analyses of Bs0-meson decays are presented. Precise measurements are performed using proton-proton collision data recorded by the LHCb experiment between 2015 and 2018. Based on the reconstruction and selection of 378 700 +/- 700 Bs0 to Ds- pi+  decays, the most precise measurement of the Bs0-Bsbar0 oscillation frequency DeltaMs = (17.7683 +/- 0.0051 +/- 0.0032) ps−1 in the world to date is achieved. This measurement alone is an essential test of the Standard Model of particle physics. In addition, it is a crucial ingredient to increase the precision of decay-time-dependent measurements of other Bs0-decay modes. The presented analysis of Bs0 to Ds K decays benefits from this updated measurement of DeltaMs and from further improvements of algorithms and methods. The CKM angle gamma = (74 +/- 11)°, an important Standard Model parameter, is measured based on 20 950 +/- 180 selected decays. Compared to the analysis using data from 2011 and 2012, the precision is improved beyond what would be expected from the increase in data sample sizes.

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