Doubly Charmful Baryonic B Decays

Abstract

There are two apparent puzzles connected with the two-body and three-body doubly charmed baryonic B decays. First, earlier calculations based on QCD sum rules or the diquark model predict $Br(\bar B^0\toΞ_c^+\barΛ_c^-)\approx Br(\bar B^0\to\B_c\bar N)$, while experimentally the former has a rate two orders of magnitude larger than the latter. Second, a naive estimate of the branching ratio $10^{-9}$ for the color-suppressed three-body decay $\bar{B}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}K$, which is highly suppressed by phase space, is too small by five to six orders of magnitude compared to experiment. We show that the great suppression for the ${\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}K$ production can be alleviated provided that there exists a narrow hidden charm bound state with a mass near the ${\Lambda }_c{\bar{\Lambda }}_c$ threshold. This new state that couples strongly to the charmed baryon pair can be searched for in B decays and in $p\bar{p}$ collisions by studying the mass spectrum of $D^{(\ast )}{\bar{D}}^{(\ast )}$ or ${\Lambda }_c{\bar{\Lambda }}_c$. The doubly charmful decay $\bar{B}\to {\Xi }_c{\bar{\Lambda }}_c$ has a configuration more favorable than the singly charmful one such as ${\bar{B}}^0\to {\Lambda }_c\bar{p}$ since no hard gluon is needed to produce the energetic ${\Xi }_c{\bar{\Lambda }}_c$ pair in the former decay, while two hard gluons are needed for the latter process. Assuming that a soft $q\bar{q}$ quark pair is produced through the $\sigma$ and $\pi$ meson exchanges in the configuration for $\bar{B}\to {\Xi }_c{\bar{\Lambda }}_c$, it is found that its branching ratio is of order $10^{-3}$, in agreement with experiment.

14 pages, 5 figures, to appear in Phys. Rev. D

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Cited by in corpus (13)

• A study of Bbar -> Xi_c Lambda_c^- and Bbar -> Lambda_c^+ Lambda_c^- Kbar decays at BABAR
• First measurements of absolute branching fractions of ${\Xi }_c^0$ at Belle
• Reconciling the X(4630) with the Y(4660)
• Study of B+ to p Lambdabar gamma, p Lambdabar pi0 and B0 to p Lambdabar pi-
• Direct CP violation in $B^{\pm }\to p\bar{p}{K}^{(\ast )\pm }$
• First measurements of absolute branching fractions of the ${\Xi }_c^{+}$ baryon at Belle
• Exclusive Baryonic B Decays Circa 2005
• On the smallness of Tree-dominated Charmless Two-body Baryonic $B$ Decay Rates
• Determination of Nucleon Form factors from Baryonic B Decays
• Search for \bar{B}^0\toΛ_c^+\barΛ_c^- decay at Belle
• Higher twist corrections to doubly-charmed baryonic $B$ decays
• Status of baryonic B decays
• Observation of the decays $B^{+}\to {\Sigma }_c(2455{)}^{++}{\overline{\Xi }}_c^{-}$ and $B^0\to {\Sigma }_c(2455{)}^0{\overline{\Xi }}_c^0$