A study of the charmless baryonic decays $B^0_{ (s)} \to K^0 p \bar{ p}$ is presented, where $B^0_{ (s)}$ denotes either a $B^0$ or a $B^0_s$ meson. The analysis is based on proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and $13~\mathrm{ Tev}$, corresponding to an integrated luminosity of $9~\mathrm{ fb}^{ -1}$. The decay $B^0_s \to K^0 p \bar{ p}$ is observed for the first time, with a measured branching fraction of $(9.14 \pm 1.69 \pm 0.90 \pm 0.33 \pm 0.20) \times 10^{ -7}$ and a significance of $5.6\sigma$. The uncertainties respectively account for statistical and systematic contributions, the precision of the branching fraction of the normalisation channel $B^0 \to K^0 \pi^{ +} \pi^{ -}$ and the fragmentation fraction ratio ${ f_s}/{ f_d}$. The branching fraction determined for $B^0 \to K^0 p \bar{ p}$ is $(2.82 \pm 0.08 \pm 0.12 \pm 0.10) \times 10^{ -6}$, which is the most precise measurement to date.
Categories: hep-ex