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Abstract

This thesis presents the measurement of the CP-violating asymmetry in B0-B0bar mixing using data corresponding to an integrated luminosity of 3.0 fb^{−1} collected at the LHCb experiment in proton-proton collisions at the center-of-mass energies of 7 TeV and 8 TeV. This analysis uses untagged, semileptonic B0 → D−μ+ν and B0 → D∗−μ+ν decays, where the D− decays into K+π−π−, and the D∗− decays into D0(→ K+π−)π−. The neutrino in the semileptonic B decays is not reconstructed. A decay time dependent fit allows to disentangle the CP asymmetry from the possible B0-B0bar production asymmetry. Detection and reconstruction asymmetries are calibrated using promptly produced Cabibbo-favored D+ decays, and inclusive secondary J/ψ decays. The CP-violating asymmetry is measured to be a^{d}_{sl} = (−0.02 ± 0.19 (stat) ± 0.30 (syst))% . This result is consistent with the Standard Model prediction, and it is the most precise measurement from a single experiment to date. This measurement is published in Physical Review Letters