The first observation of the singly Cabibbo-suppressed ${\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{K}^{+}$ and ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+}$ decays is reported, using proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be $\frac{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{K}^{+})}{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})}=[6.08\pm 0.51(\mathrm{stat})\pm 0.40(\mathrm{syst})]\%,\frac{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+})}{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})}=[15.81\pm 0.87(\mathrm{stat})\pm 0.44(\mathrm{syst})\pm 0.16(\mathrm{ext})]\%.$ In addition, using the ${\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+}$ decay channel, the ${\mathrm{\Omega }}_c^0$ baryon mass is measured to be $M({\mathrm{\Omega }}_c^0)=2695.28\pm 0.07(\mathrm{stat})\pm 0.27(\mathrm{syst})\pm 0.30(\mathrm{ext})\mathrm{MeV},$ improving the precision of the previous world average by a factor of 4.

• Received 17 August 2023
• Accepted 28 November 2023

DOI:https://doi.org/10.1103/PhysRevLett.132.081802

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