Evidence for the singly Cabibbo-suppressed decay ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+}$ and search for ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{K}^{+}$ and ${\mathrm{\Omega }}^{-}{K}^{+}$ decays at Belle

Using a data sample of 980 fb${}^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, we study for the first time the singly Cabibbo-suppressed decays ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+}$ and ${\mathrm{\Omega }}^{-}{K}^{+}$ and the doubly Cabibbo-suppressed decay ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{K}^{+}$. Evidence for an ${\mathrm{\Omega }}_c^0$ signal in the ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+}$ mode is reported with a significance of $4.5\sigma$ including systematic uncertainties. The ratio of branching fractions to the normalization mode ${\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+}$ is measured to be $$\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+})\mathrm{/}\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})=0.253\pm 0.053(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{.})\pm 0.030(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{.})\mathrm{.}$$ No significant signals of ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{K}^{+}$ and ${\mathrm{\Omega }}^{-}{K}^{+}$ modes are found. The upper limits at $90\mathrm{\%}$ confidence level on ratios of branching fractions are determined to be $$\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{K}^{+})\mathrm{/}\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})<0.070$$ and $$\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{K}^{+})\mathrm{/}\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})<\mathrm{0.29.}$$