Study of ${\Lambda }_b^0$ and ${\Xi }_b^0$ decays to $\Lambda h^{+}{h}^{{}^{\mathrm{\prime }}-}$ and evidence for $CP$ violation in ${\Lambda }_b^0\to \Lambda K^{+}{K}^{-}$ decays

A study of ${\Lambda }_b^0$ and ${\Xi }_b^0$ decays to $\Lambda h^{+}{h}^{\mathrm{\prime }-}$ $(h^{(\mathrm{\prime })}=\pi ,K)$ is performed using $pp$ collision data collected by the LHCb experiment during LHC Runs 1$-$2, corresponding to an integrated luminosity of $9{\mathrm{f}\mathrm{b}}^{-1}$. The branching fractions for these decays are measured using the ${\Lambda }_b^0\to {\Lambda }_c^{+}(\to \Lambda {\pi }^{+}){\pi }^{-}$ decay as control channel. The decays ${\Lambda }_b^0\to \Lambda {\pi }^{+}{\pi }^{-}$ and ${\Xi }_b^0\to \Lambda K^{-}{\pi }^{+}$ are observed for the first time. For decay modes with sufficient signal yields, $CP$ asymmetries are measured in the full and localized regions of the final-state phase space. Evidence is found for $CP$ violation in the ${\Lambda }_b^0\to \Lambda K^{+}{K}^{-}$ decay, interpreted as originating primarily from an asymmetric ${\Lambda }_b^0\to N^{\ast +}{K}^{-}$ decay amplitude. The measured $CP$ asymmetries for the other decays are compatible with zero.