Testing the Standard Model in rare decays of $B$ mesons at the Belle experiment

Rare decays of B mesons are an ideal probe to search for phenomena beyond the Standard Modelof particle physics, since contributions from new particles can aect the decays on the same level asStandard Model predictions. The rare decay of B ! K*ll oers the quark transition b ! sll, a avorchanging neutral current which is forbidden at tree level in the Standard Model. Higher order processessuch as penguin diagrams allow for these processes, leading to branching ratios of less than one in amillion. Various extensions to the Standard Model predict inuences of new physics, which can enhance orsuppress branching ratios or lead to changes in angular distributions of the decay products. We probe theB ! K*ll decay for deviations from Standard Model predictions and perform lepton avour universalitytests using the data of the Belle experiment