Observation of the baryonic $B$ decay ${\overline{B}}^0\to {\Lambda }_c^{+}\overline{\Lambda }{K}^{-}$

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

Figure 1

The $\Delta E$ distribution for ${\Lambda }_c^{+}\overline{\Lambda }{K}^{-}$ candidates in the data with all selection criteria applied (points). The solid line is the overall fit result, while the dashed line is the background component.

Figure 2

The $m({\Lambda }_c^{+}\overline{\Lambda })$, $m(\overline{\Lambda }{K}^{-})$, and $m({\Lambda }_c^{+}{K}^{-})$ distributions in the data (points) in comparison with the Monte Carlo sample (red histogram).

Figure 3

The background-subtracted $m({\Lambda }_c^{+}\overline{\Lambda })$, $m(\overline{\Lambda }{K}^{-})$, and $m({\Lambda }_c^{+}{K}^{-})$ distributions for the data (points) and for the final weighted Monte Carlo sample (red histogram).