Časově závislé narušení CP symetrie v rozpadech B0 → ηc KS0 na experimentu Belle, Alignment detektoru Belle II

Bilka, Tadeáš

This thesis deals with two independent yet closely related topics. In the first part, a measurement of branching fraction and time-dependent CP violation in B0 → ηcK0 S, ηc → K0 SK± π∓ decays is performed. This decay allows access to sin 2ϕ1, where ϕ1 is an angle of the unitary triangle of the Cabibbo-Kobayashi- Maskawa quark mixing matrix. The measurement is based on the entire dataset of the Belle experiment, which consists of 772 × 106 B meson pairs collected at the KEKB e+ e− collider. The extracted mixing-induced and direct CP- violation parameters read sin 2ϕ1 ≃ S = 0.59 ± 0.17 (stat) ± 0.07 (syst) and A = 0.16 ± 0.12 (stat) ± 0.06 (syst), respectively. The measured product of branching fractions B(B0 → ηcK0 S) × B(ηc → K0 SK± π∓ ) is (9.8 ± 0.6 (stat) ± 0.4 (syst)±2.3 (int))×10−6 , where the last uncertainty accounts for interference with non-resonant background. The second part deals with the alignment of the vertex detector and the central drift chamber of the Belle II experiment at the SuperKEKB collider, which is a next-generation Super-B-Factory. With the new pixel detector and the presented alignment method, Belle II achieves approximately twice better impact parameter resolutions than Belle. The presented alignment procedure involves a simultaneous determination of about sixty thousand...

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