Semileptonic baryonic $B$ decays

We study the semileptonic $B\to \mathbf{B}{\bar{\mathbf{B}}}^{\mathbf{\prime }}L{\bar{L}}^{\mathrm{\prime }}$ decays with $\mathbf{B}{\bar{\mathbf{B}}}^{\mathbf{\prime }}$ ($L{\bar{L}}^{\mathrm{\prime }}$) representing a baryon (lepton) pair. Using the new determination of the $B\to \mathbf{B}{\bar{\mathbf{B}}}^{\mathbf{\prime }}$ transition form factors, we obtain $\mathcal{B}(B^{-}\to p\bar{p}{\mu }^{-}{\bar{\nu }}_{\mu })=(5.4\pm 2.0)\times {10}^{-6}$ agreeing with the current data. Besides, $\mathcal{B}(B^{-}\to \mathrm{\Lambda }\bar{p}\nu \bar{\nu })=(3.5\pm 1.0)\times {10}^{-8}$ is calculated to be 20 times smaller than the previous prediction. In particular, we predict $\mathcal{B}({\bar{B}}_s^0\to p\bar{\mathrm{\Lambda }}{e}^{-}{\bar{\nu }}_e,p\bar{\mathrm{\Lambda }}{\mu }^{-}{\bar{\nu }}_{\mu },p\bar{\mathrm{\Lambda }}{\tau }^{-}{\bar{\nu }}_{\tau })=(2.1\pm 0.6,2.1\pm 0.6,1.7\pm 1.0)\times {10}^{-6}$ and $\mathcal{B}({\bar{B}}_s^0\to \mathrm{\Lambda }\bar{\mathrm{\Lambda }}\nu \bar{\nu })=(0.8\pm 0.2)\times {10}^{-8}$, which can be accessible to the LHCb experiment.