Measurements of the branching fractions $\mathcal{B}\mathbf{(}{B}^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c^{\prime 0}\mathbf{)}$, $\mathcal{B}\mathbf{(}{B}^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c\mathbf{(}2645{)}^0\mathbf{)}$ and $\mathcal{B}\mathbf{(}{B}^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c\mathbf{(}2790{\mathbf{)}}^0\mathbf{)}$

Using the data sample of $711{\mathrm{fb}}^{-1}$ of $\mathrm{\Upsilon }(4S)$ on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c^{\prime 0}$, $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2645{)}^0$, and $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2790{)}^0$. The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against ${\overline{\mathrm{\Lambda }}}_c^{-}$ baryons in selected $B^{-}$ candidates. The branching fraction of $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2790{)}^0$ is measured to be $(1.1\pm 0.4\pm 0.2)\times {10}^{-3}$, where the first uncertainty is statistical and the second is systematic. The 90% credibility level upper limits on $\mathcal{B}(B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c^{\prime 0})$ and $\mathcal{B}(B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2645{)}^0)$ are determined to be $6.5\times {10}^{-4}$ and $7.9\times {10}^{-4}$, respectively.

Figure 1

$\mathrm{\Delta }{E}^{\mathrm{tag}}$ distribution summed over the two reconstructed ${\overline{\mathrm{\Lambda }}}_c^{-}$ decay modes. The points with error bars represent the data, the solid curve is the best-fit result, and the blue dashed curve is the fitted background. The red dashed lines show the defined $\mathrm{\Delta }{E}^{\mathrm{tag}}$ signal region.

Figure 2

Scatter plot of $M_{{\overline{\mathrm{\Lambda }}}_c^{-}}$ of signal side vs $M_{\mathrm{bc}}^{\mathrm{tag}}$ of $B_{\mathrm{tag}}^{+}$ in the ${\mathrm{\Xi }}_c^{*0}$ signal region, i.e., $2.5\mathrm{GeV}/c^2<M_{B_{\mathrm{tag}}^{+}{\overline{\mathrm{\Lambda }}}_c^{-}}^{\mathrm{rec}}<2.86\mathrm{GeV}/c^2$. The solid box shows the selected signal region, and the blue and red dashed boxes define the $M_{\mathrm{bc}}^{\mathrm{tag}}$ and $M_{{\overline{\mathrm{\Lambda }}}_c^{-}}$ sidebands described in the text.

Figure 3

$M_{B_{\mathrm{tag}}^{+}{\overline{\mathrm{\Lambda }}}_c^{-}}^{\mathrm{rec}}$ distribution of selected candidate events. The points with error bars represent the data, the solid blue curve is the best fit, the dashed curve is the fitted total background, and the cyan shaded histogram is the normalized distribution of the $M_{\mathrm{bc}}^{\mathrm{tag}}$ and $M_{{\overline{\mathrm{\Lambda }}}_c^{-}}$ sideband events (see Fig. 2).