Gholipourverki, Sahar2024-09-032024-09-032024https://hdl.handle.net/1828/20356Semileptonic B meson decays provide a direct method to measure the parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, which is essential for understanding quark mixing and CP violation in the Standard Model. This thesis presents an exploratory study on the Branching Fraction of the B meson decay mode [character cannot be represented] which has never been measured. Here, ℓ represents either an electron or a muon, νℓ denotes the corresponding lepton neutrino, D(∗) refers to either a D meson or its excited state D∗, and η symbolizes the eta meson. In this analysis to reduce the significantly higher occurrence of background events compared to signal candidates, both B mesons are reconstructed semileptonically. The tag-side B meson predominantly decays via [character cannot be represented]. This investigation aims to contribute to a more comprehensive understanding of B meson semileptonic decays by attempting to bridge the gap between the measurements of exclusive semileptonic decay modes and the summation of all measured exclusive semileptonic decays, and improve the understanding of the background in lepton flavor-violating decay modes such as B → D(∗)τντ . This work shows that with 470.78 fb−1, with the MC BF([character cannot be represented]) + BF([character cannot be represented]) = 0.008 where ℓ can be either an electron or a muon, Belle II may be able to measure sum of the branching fraction for the decay of [character cannot be represented] and B− → D[character cannot be represented] with more than 5σ significance.enAvailable to the World Wide WebParticle physicsThesis