Observation of Cabibbo-Suppressed Two-Body Hadronic Decays and Precision Mass Measurement of the ${\mathrm{\Omega }}_c^0$ Baryon

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 $13\mathrm{T}\mathrm{e}\mathrm{V}$, corresponding to an integrated luminosity of $5.4{\mathrm{f}\mathrm{b}}^{-1}$, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be $\frac{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{K}^{+})}{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})}=[6.08\pm 0.51(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.40(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})]\mathrm{\%}$, $\frac{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+})}{\mathcal{B}({\mathrm{\Omega }}_c^0\to {\mathrm{\Omega }}^{-}{\pi }^{+})}=[15.81\pm 0.87(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.44(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\pm 0.16(\mathrm{e}\mathrm{x}\mathrm{t})]\mathrm{\%}$. 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 $M({\mathrm{\Omega }}_c^0)=2695.28\pm 0.07(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.27(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\pm 0.30(\mathrm{e}\mathrm{x}\mathrm{t})\mathrm{M}\mathrm{e}\mathrm{V}$, improving the precision of the previous world average by a factor of 4.