Measurement of the $CP$ asymmetry in $B^{-}\to D_s^{-}{D}^0$ and $B^{-}\to D^{-}{D}^0$ decays

The $CP$ asymmetry in $B^{-}\to D_s^{-}{D}^0$ and $B^{-}\to D^{-}{D}^0$ decays is measured using LHCb data corresponding to an integrated luminosity of 3.0 fb${}^{-1}$, collected in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. The results are $A^{CP}(B^{-}\to D_s^{-}{D}^0)=(-0.4\pm 0.5\pm 0.5)\mathrm{\%}$ and $A^{CP}(B^{-}\to D^{-}{D}^0)=(2.3\pm 2.7\pm 0.4)\mathrm{\%}$, where the first uncertainties are statistical and the second systematic. This is the first measurement of $A^{CP}(B^{-}\to D_s^{-}{D}^0)$ and the most precise determination of $A^{CP}(B^-\to D^-D^0)$\mathrm{.}Neitherresultshowsevidenceof$CP$ violation.