Search for ${\overline{B}}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}{\overline{\ensuremath{\Lambda}}}_{c}^{\ensuremath{-}}$ decay at Belle

Rapid Communication

Search for ${\bar{B}}^{0} \to Λ_{c}^{+} {\bar{Λ}}_{c}^{-}$ decay at Belle

Y. Uchida et al. (Belle Collaboration)

Phys. Rev. D 77, 051101(R) – Published 6 March 2008

Abstract

We search for the doubly charmed baryonic decay ${\bar{B}}^{0} \to Λ_{c}^{+} {\bar{Λ}}_{c}^{-}$ , in a data sample of $520 \times 10^{6}$ $B \bar{B}$ events accumulated at the $Υ (4 S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider. We find no significant signal and set an upper limit of $B ({\bar{B}}^{0} \to Λ_{c}^{+} {\bar{Λ}}_{c}^{-}) < 6.2 \times 10^{- 5}$ at 90% confidence level. The result is significantly below a naive extrapolation from $B (B^{-} \to Ξ_{c}^{0} {\bar{Λ}}_{c}^{-})$ assuming a simple Cabibbo-suppression factor of $| V_{c d} / V_{c s} |^{2}$ . The small branching fraction may be attributed to a suppression due to the large momentum of the baryonic decay products, which has been observed in other charmed baryonic two-body $B$ decays.