Observation of the baryonic B decay B¯0→Λc+Λ¯K−

Le résumé fourni par la source

We report the observation of the baryonic $B$ decay ${\overline{B}}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}\overline{\ensuremath{\Lambda}}{K}^{\ensuremath{-}}$ with a significance larger than 7 standard deviations based on $471\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. We measure the branching fraction for the decay ${\overline{B}}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}\overline{\ensuremath{\Lambda}}{K}^{\ensuremath{-}}$ to be $(3.8\ifmmode\pm\else\textpm\fi{}{0.8}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.2}_{\mathrm{sys}}\ifmmode\pm\else\textpm\fi{}{1.0}_{{\ensuremath{\Lambda}}_{c}^{+}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. The uncertainties are statistical, systematic, and due to the uncertainty in the ${\ensuremath{\Lambda}}_{c}^{+}$ branching fraction. We find that the ${\ensuremath{\Lambda}}_{c}^{+}{K}^{\ensuremath{-}}$ invariant-mass distribution shows an enhancement above $3.5\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.

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