Study of charmless two-body baryonic $B$ decays

We study the charmless two-body decays of $B\to {\bf B}_n \overline{\bf B}_n^\prime$ with $B = ( B^+ , B^0 , B^0_s)$ and ${\bf B}_n^{(\prime)}$ the low-lying octet baryons. The factorizable amplitudes are calculated by the modified bag model, while the nonfactorizable ones are extracted from the experimental data with the $SU(3)_F$ flavor symmetry. We are able to explain all current experimental measurements and provide predictions on the decay branching ratios in $B\to {\bf B}_n \overline{\bf B}_n^\prime$. Particularly, we find that ${\cal B}(B_s^0 \to \Xi^0 \overline{\Xi}^0) = (19.3\pm 2.7 )\times 10^{-7}$ and ${\cal B}(B_s^0 \to \Xi^- \overline{\Xi}^-) = (19.4\pm 2.7 )\times 10^{-7}$, which are sizable and able to be observed in the ongoing experiments at LHCb and BELLE-II. Furthermore, the decay branching ratios of $B_s^0 \to (p\overline{p}, n\overline{n})$ and $B^0 \to (\Xi^0 \overline{\Xi}^0 ,\Sigma^+\overline{\Sigma}^+)$ are expected to be $O(10^{-10})$, which are suppressed due to the angular momentum conservation and chiral symmetry.