Evidence for the singly Cabibbo-suppressed decay $\Omega^0_c\to\Xi^-\pi^+$ and search for $\Omega^0_c\to\Xi^-K^+$ and $\Omega^-K^+$ 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 $\Omega^0_c\to\Xi^{-}\pi^{+}$ and $\Omega^-K^+$ and the doubly Cabibbo-suppressed decay $\Omega^0_c\to \Xi^- K^{+}$. Evidence for an $\Omega^0_c$ signal in the $\Omega^0_c\to\Xi^-\pi^+$ mode is reported with a significance of $4.5\sigma$ including systematic uncertainties. The ratio of branching fractions to the normalization mode $\Omega_c^0\to \Omega^-\pi^+$ is measured to be $${\cal B}(\Omega_{c}^{0} \to \Xi^{-} \pi ^{+} )/{\cal B}(\Omega_c^0\to \Omega^-\pi^+)=0.253\pm 0.053({\rm stat.})\pm 0.030({\rm syst.}).$$ No significant signals of $\Omega^0_c\to\Xi^-K^+$ and $\Omega^-K^+$ modes are found. The upper limits at $90\%$ confidence level on ratios of branching fractions are determined to be $${\cal B}(\Omega_{c}^{0} \to \Xi^{-} K ^{+})/{\cal B}(\Omega_c^0\to \Omega^-\pi^+) < 0.070$$ and $${\cal B}(\Omega_{c}^{0} \to \Omega^{-}K^{+})/{\cal B}(\Omega_c^0\to \Omega^-\pi^+) < 0.29.$$