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

Abstract

Abstract 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 ¯ ′ $$ B\to {\mathbf{B}}_c\overline{\mathbf{B}}^{\prime } $$ 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 ¯ ′ $$ \overline{\mathbf{B}}^{\prime } $$ an octet charmless (anti-)baryon. In particular, we calculate that ℬ B ¯ 0 → Σ c + p ¯ = 2.9 − 0.9 + 0.8 × 10 − 6 $$ \mathrm{\mathcal{B}}\left({\overline{B}}^0\to {\Sigma}_c^{+}\overline{p}\right)=\left({2.9}_{-0.9}^{+0.8}\right)\times {10}^{-6} $$ in good agreement with the experimental upper bound. Its cousin B ¯ s 0 $$ {\overline{B}}_s^0 $$ mode, B ¯ s 0 → Λ c + p ¯ $$ {\overline{B}}_s^0\to {\Lambda}_c^{+}\overline{p} $$ , 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 $$ \mathrm{\mathcal{B}}\left({\overline{B}}_s^0\to {\Lambda}_c^{+}\overline{p}\right)=\left(0.8\pm 0.3\right)\times {10}^{-6} $$ , 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 $$ \mathrm{\mathcal{B}}\left({\overline{B}}^0\to {\Xi}_c^{+}{\overline{\Sigma}}^{-}\right)=\left(1.1\pm 0.4\right)\times {10}^{-5} $$ , can be tested with future Belle II measurements.

Keywords

• B physics
• Branching fraction
• Flavor physics
• Rare decay
• Hadron-Hadron scattering (experiments)