부산대학교 도서관

In this thesis, an angular analysis of B0 → K∗0μ+μ− decays is presented. The angluar and the invariant dimuon mass squared (q2) distributions are parameterised in an unbinned maximum likelihood fit. The signal model is based on the decay amplitudes of B0 → K∗0μ+μ− decays, including the penguin amplitudes and the amplitudes involving hadronic resonances, i.e. B0 → V (→ μ+μ−)K∗0 decays, where V are cc vector resonances, such as the J/ψ. Fitting for the decay amplitudes directly allows for the determination of the vector and pseudo-vector coupling constants C9 and C10 from data. These can be compared to Standard Model (SM) calculations in order to search for New Physics (NP) beyond the SM. Since both the penguin amplitudes and the hadronic amplitudes are included in the model, the interference between them can be determined directly from data. The level of interference between the resonant amplitudes and the penguin amplitudes in B0 → K∗0μ+μ− decays has never been measured before and cannot be predicted from first principles in the SM. Due to that lack of knowledge, the SM predictions of B0 → K∗0μ+μ− decays are currently not fully trusted in the particle physics community. This holds back the interpretation of the discrepancies between the measured q2-binned angular observables of B0 → K∗0μ+μ− decays [1] and the SM predictions, as clear indication of NP. The fit presented in this thesis is intended to help to solve this issue. The parameterisation of the background events is complex for this analysis due to a kinematic constraint applied to all events, which causes a distortion of the background. A novel background fitting procedure and new correction techniques are presented in this thesis. While the full dataset, which will be used for the planned publication, is not available yet, a preliminary fit to the 2011 and 2012 data, corresponding to approximately 3 fb−1 of integrated luminosity, is presented in this thesis to demonstrate the ability of the model to describe the data. The fit results also provide a first indication, that the discrepancy between experiment and SM still persists in the angular and q2 distributions of B0 → K∗0μ+μ− decays, despite a sizeable contribution from the interference of the hadronic amplitudes with the penguin amplitudes.