BOUBAA, DRIS2020-09-162020-09-162018-03-11http://hdl.handle.net/123456789/1279One of the most promising signals of new physics at colliders is the rare decay B ! + . If the observation of B ! + occurs at present experiments, it would be a clear sign of new physics. In this regards, we calculate this process in an extended Higgs sector framework where the decay is mediated by the exchange of spin zero particle with avour changing neutral current couplings. If we identify the scalar with the newly discovered state at LHC with a mass 125 GeV then we nd that, after imposing all experimental constraints, the BR(Bs ! + ) can be as high 10􀀀6 and BR(Bd ! + ) can be as high as 10􀀀7. We also calculate this process in the minimal supersymmetric standard model and nd the BR(Bs ! + ) is typically of the order 10􀀀8. Also, we study the processes B ! D and B ! D on the light of a deviation from the standard model expectations which has been recently reported by BaBar, Belle and LHCb. Since these processes are all tree-level decays in the SM, it is di cult to explain this deviation with models of new physics. Thus, we show that supersymmetric e ects driven by penguin contributions to the b ! c transition are able to account simultaneously for a signi cant increase of both branching ratios of B ! D and B ! D with respect to the Standard Model predictions, thereby approaching their experimentally measured values. We emphasis that a degeneracy between the lightest chargino and neutralino, with masses less than 300 GeV, in addition to a large stau/snueutrino mass and a large tan are essential for enhancing the e ect of the lepton penguin W , which is responsible for the improved theoretical predictions with respect to current data.