High-precision measurements of charge asymmetries at LHCb

To explain the imbalance between matter and antimatter, an additional source of $C\!P$ symmetry violation is needed in addition to the Standard Model. This new force can affect observables related to $C\!P$ violation, leading to deviations between direct measurements and their Standard Model predictions. The D0 collaboration reported such a deviation in the $C\!P$ violation of B mixing. This thesis presents a measurement of $C\!P$ violation in $B_{s}^{0}$ mixing, which is the most precise to date. While this measurement a priori seems like a straight-forward counting experiment, the inferred asymmetries are spoiled in the case that the reconstruction efficiency of the $B_{s}^{0}$ decay products differs from that of the $\overline{B}_{s}^{0}$, which is realistic. The level of precision required for a competitive measurement of $C\!P$ violation in $B_{s}^{0}$ mixing turns the determination of the instrumental effects into a delicate experimental challenge. The resulting, corrected, value for the measurement presented in this thesis is \[ a_{\mathrm{sl}}^{s} = (0.39 \pm 0.26 \pm 0.20)\% \] It became clear that due to limitations of the applied methods, the precision of this measurement would not increase in the near future despite the additional data. Therefore, this dissertation focuses on new techniques to perform such measurements with the needed precision to interpret the larger data sets expected with Run 2 and the upgrades of LHCb.