First observation of $B^0\rightarrow\overline{D}^{*}(2007)^0K^+\pi^-$ and $B_s^0\rightarrow\overline{D}^{*}(2007)^0K^-\pi^+$ decays in LHCb

Measurements of the $\gamma$ angle of the unitarity triangle formed from elements of the CKM matrix are achieved through the study of $B$ hadron decays featuring interference between $b\rightarrow c\overline{u}s$ and $b\rightarrow u\overline{c}s$ processes. Such measurements are affected by a systematic uncertainty due to the limited knowledge of yet to be observed partially reconstructed decays featuring soft neutral final state particles. Unless knowledge of these decays is improved, the precision of future determination of $\gamma$ may become limited by this source of uncertainty. In this thesis such decays are studied, resulting in the first observation of $B^0\rightarrow\overline{D}^{*}(2007)^0K^+\pi^-$ and $B_s^0\rightarrow\overline{D}^{*}(2007)^0K^-\pi^+$ decays, and measurements of their branching fractions with respect of that of $B^0\rightarrow\overline{D}^{*}(2007)^0\pi^+\pi^-$ decays. In addition, results on the phase space distribution of such decays are given, which directly benefit the understanding of these decays as partially reconstructed backgrounds in measurements of $\gamma$ in $B^+\rightarrow D K^+$ and $B^0\rightarrow D K^+\pi^-$ decay studies. The $B^0\rightarrow\overline{D}^{*}(2007)^0K^+\pi^-$ and $B_s^0\rightarrow\overline{D}^{*}(2007)^0K^-\pi^+$ decay channels also provide interesting insight for the study of resonances in the charm sector and could themselves be used in the future for determinations of $\gamma$. The study presented in this thesis is based on the data recorded by the LHCb experiment during the years from 2016 to 2018, corresponding to a sample of $5.4\rm~ fb^{-1}$. It constitutes the first analysis within the LHCb collaboration featuring fully reconstructed $D^*(2007)^0\rightarrow D^0\gamma$ and $D^*(2007)^0\rightarrow D^0\pi^0$ decays, and pioneers the usage of a novel weighting method while implementing an event-by-event efficiency correction to account for resonant structures in the decays under study.