Measurement of branching fractions and $CP$ asymmetries in ${\Lambda }_b^0({\Xi }_b^0)\text{\hspace{0.17em}⁣}\to p{K}_{\mathrm{S}}^0{h}^{-}$ decays

A study of ${\Lambda }_b^0$ and ${\Xi }_b^0$ baryon decays to the final states $p{K}_{\mathrm{S}}^0{\pi }^{-}$ and $p{K}_{\mathrm{S}}^0{K}^{-}$ is performed using $pp$ collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $9{\mathrm{f}\mathrm{b}}^{-1}$. The decays ${\Lambda }_b^0\text{\hspace{0.17em}⁣}\to p{K}_{\mathrm{S}}^0{K}^{-}$ and ${\Xi }_b^0\text{\hspace{0.17em}⁣}\to p{K}_{\mathrm{S}}^0{K}^{-}$ are observed for the first time, with significances reaching eight standard deviations. The branching fractions and integrated $CP$ asymmetries are measured for the ${\Lambda }_b^0\text{\hspace{0.17em}⁣}\to p{K}_{\mathrm{S}}^0{\pi }^{-}$, ${\Lambda }_b^0\text{\hspace{0.17em}⁣}\to p{K}_{\mathrm{S}}^0{K}^{-}$, and ${\Xi }_b^0\text{\hspace{0.17em}⁣}\to p{K}_{\mathrm{S}}^0{K}^{-}$ decays. For the decay ${\Lambda }_b^0\text{\hspace{0.17em}⁣}\to p{K}_{\mathrm{S}}^0{\pi }^{-}$, the $CP$ asymmetries are measured in different regions of the Dalitz plot. No evidence of $CP$ violation is observed.