Feasibility study for the measuring of the CKM phases gamma and delta gamma in decays of neutral B-mesons with the ATLAS detector

This thesis contains a study of the possible measurement of parameters of the Standard Model which relate to $CP$ violation with the ATLAS detector. This is done in two specific neutral $B$-meson channels. The first analysis presents a feasibility study for extracting the notoriously difficult to measure third angle of the unitarity triangle $\gamma$ from neutral $B_d$ decays of the type $B^0_d \rightarrow D^0 K^{0*}$. The small number of signal events that can be reconstructed after three years of running at low luminosity and the huge combinatorial background expected lead to the conclusion that this method would not result in a viable measurement of $\gamma$ with the ATLAS detector, unless the observed branching fractions for these channels were found to be considerably greater than currently expected. The second analysis presents results for the $B^0_s \rightarrow J/\psi \phi$ decay modes, yielding the weak phase $\delta \gamma$ and several unmeasured parameters of the neutral $B^0_s$-system. The reconstruction efficiencies and parameter resolutions obtained, have been used to show that the available statistics would be enough to measure $\Delta \Gamma_s$, $\overline{\Gamma}_s$ and the $CP$ amplitudes $A_{\parallel}$ and $A_{\perp}$ with relative statistical errors of the order of a few percent. These results also showed that a measurement of the weak phase will have a statistical accuracy similar to the expected value for $\delta \gamma$ in the Standard Model. The main reason for this is found to be poor tagging quality of the standard approaches. A new SST method, based on probability theory is proposed.