Charmful Baryonic B Decays ${\bar{B}}^0\to {\Lambda }_c\bar{p}$ and $\bar{B}\to {\Lambda }_c\bar{p}\pi (\rho )$

Abstract

We study the two-body and three-body charmful baryonic B decays: ${\bar{B}}^0\to {\Lambda }_c\bar{p}$ and $\bar{B}\to {\Lambda }_c\bar{p}\pi (\rho )$. The factorizable W-exchange contribution to ${\bar{B}}^0\to {\Lambda }_c\bar{p}$ is negligible. Applying the bag model to evaluate the baryon-to-baryon weak transition matrix element, we find $B({\bar{B}}^0\to {\Lambda }_c\bar{p})\le 1.1\times 10^{-5}|g_{B^{0}p{\Sigma }_b^{+}}/6{|}^2$ with $g_{B^{0}p{\Sigma }_b^{+}}$ being a strong coupling for the decay ${\Sigma }_b^{+}\to {\bar{B}}^{0}p$ and hence the predicted branching ratio is well below the current experimental limit. The factorizable contributions to $B^{-}\to {\Lambda }_c\bar{p}{\pi }^{-}$ can account for the observed branching ratio of order $6\times 10^{-4}$. The branching ratio of order $2\times 10^{-3}$ for $B^{-}\to {\Lambda }_c\bar{p}{\rho }^{-}$ is larger than that of $B^{-}\to {\Lambda }_c\bar{p}{\pi }^{-}$ by a factor of about 2.6. We explain why the three-body charmful baryonic B decay has a larger rate than the two-body one, contrary to the case of mesonic B decays.

Comments: 17 pages, 2 figures. Form factors for Lambda_c-p transitions are corrected. Strong couplings are slightly modified. To appear in Phys. Rev. D