Measurements of $CP$ asymmetries and branching fraction ratios of $B^{-}$ decays to two charm mesons

The $CP$ asymmetries of seven $B^{-}$ decays to two charm mesons are measured using data corresponding to an integrated luminosity of $9{\text{ fb}}^{-1}$ of proton-proton collisions collected by the LHCb experiment. Decays involving a $D^{\ast 0}$ or $D_s^{\ast -}$ meson are analysed by reconstructing only the $D^0$ or $D_s^{-}$ decay products. This paper presents the first measurement of ${\mathcal{A}}^{CP}(B^{-}\to D_s^{\ast -}{D}^0)$ and ${\mathcal{A}}^{CP}(B^{-}\to D_s^{-}{D}^{\ast 0})$, and the most precise measurement of the other five $CP$ asymmetries. There is no evidence of $CP$ violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured.