Search for Baryon-Number-Violating Processes in $B^{-}$ Decays to the ${\bar{\mathrm{\Xi }}}_c^0{\bar{\mathrm{\Lambda }}}_c^{-}$ Final State

We report the results of the first search for $B^{-}$ decays to the ${\bar{\mathrm{\Xi }}}_c^0{\bar{\mathrm{\Lambda }}}_c^{-}$ final state using 711~$\mathrm{f}{\mathrm{b}}^{-1}$ of data collected at the $\mathrm{{\rm Y}}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The results are interpreted in terms of both direct baryon-number-violating $B^{-}$ decay and ${\mathrm{\Xi }}_c^0-{\bar{\mathrm{\Xi }}}_c^0$ oscillations which follow the Standard Model decay $B^{-}\to {\mathrm{\Xi }}_c^0{\bar{\mathrm{\Lambda }}}_c^{-}$. We observe no evidence for baryon number violation and set the 95% confidence-level upper limits on the ratio of baryon-number-violating and Standard Model branching fractions $\mathcal{B}(B^{-}\to {\bar{\mathrm{\Xi }}}_c^0{\bar{\mathrm{\Lambda }}}_c^{-})\mathrm{/}\mathcal{B}(B^{-}\to {\mathrm{\Xi }}_c^0{\bar{\mathrm{\Lambda }}}_c^{-})$ to be $<2.7\mathrm{\%}$ and on the ${\mathrm{\Xi }}_c^0-{\bar{\mathrm{\Xi }}}_c^0$ oscillation angular frequency $\omega$ to be $<0.76{\mathrm{p}\mathrm{s}}^{-1}$ (equivalent to ${\tau }_{\mathrm{m}\mathrm{i}\mathrm{x}}>1.3$~ps).