Thesis defense of Vukan Jevtic

This thesis presents CP-violation measurements conducted with data recorded by the LHCb detector during the Run 2 data-taking phase of the LHC. The size of the data set corresponds to an integrated luminosity of 6fb^−1 . A time-dependent measurement of the CP asymmetry arising in decays of neutral B mesons to CP-invariant final states is performed in three decay channels: B→J/ψ(→μ+μ-)KS, B→J/ψ(→e+e-)KS and B→ψ(2S)(→μ+μ-)KS. The KS mesons are reconstructed in decays to two oppositely charged pions. A combined fit to the Run 2 data set of LHCb is performed in the three analyzed channels and gives the result
S = 0.717 +- 0.013 (stat) +- 0.008 (syst),
C = 0.008 +- 0.012 (stat) +- 0.003 (syst).
This result is more precise than the previous world averages of these parameters, making this measurement the most precise single measurement of the quantity S to date. The parameter S is related to the CKM angle β, which parametrizes CP violation in the Standard Model of particle physics. The result is consistent with previous measurements from the LHCb collaboration and the B-factories Belle and BaBar.

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