Thesis defense of Antje Mödden

Precision measurements of CKM-matrix elements are used to test the Standard Model of particle physics. Decays of Bs0 mesons that proceed via b→ ccs transitions are used to measure the CP -violating weak mixing phase φs that is directly related to the CKM angle βs and has a precise theoretical prediction. The mixing phase φs can be measured using Bs0 → Ds+Ds− decays, where higher-order Standard Model effects can be assessed by exploiting results from analyses in additional decays of the B → DD family. These analyses comprise CP -violation and branching-ratio measurements. Two different analyses of B → DD decays are presented, which utilise data collected by the LHCb experiment.

A search for the Bs0 → D∗±D∓ decay is presented using data corresponding to an integrated luminosity of 9 fb−1 collected at centre-of-mass energies of 7, 8 and 13 TeV. The Bs0 → D∗±D∓ decay is observed and its branching fraction is measured for the first time.

The ongoing measurement of CP violation in Bs0 → Ds+Ds− decays uses data corresponding to 6 fb−1 collected at 13 TeV. The measurement of the CP parameters is still kept blind, but the sensitivities to the CP parameters are evaluated and indicate that this will be the most precise measurement in this decay channel.

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