Testing the W -exchange mechanism with two-body baryonic B decays.

The role of W -exchange diagrams in baryonic B decays is poorly understood, and often taken as insignificant and neglected. We show that charmful two-body baryonic B → B c B ¯ ′ decays provide a good test-bed for the study of the W -exchange topology, whose contribution is found to be non-negligible; here B_c is an anti-triplet or a sextet charmed baryon, and B ¯ ′ an octet charmless (anti-)baryon. In particular, we calculate that ℬ B ¯ 0 → Σ c + p ¯ = 2.9 − 0.9 + 0.8 × 10 − 6 in good agreement with the experimental upper bound. Its cousin B ¯ s 0 mode, B ¯ s 0 → Λ c + p ¯ , is a purely W -exchange decay, hence is naturally suited for the study of the role of the W -exchange topology. We predict ℬ B ¯ s 0 → Λ c + p ¯ = 0.8 ± 0.3 × 10 − 6 , a relatively large branching ratio to be tested with a future measurement by the LHCb collaboration. Other predictions, such as ℬ B ¯ 0 → Ξ c + Σ ¯ − = 1.1 ± 0.4 × 10 − 5 , can be tested with future Belle II measurements. [ABSTRACT FROM AUTHOR]