Measurement of branching fractions of singly Cabibbo-suppressed decays ${\Lambda }_{c}^{+}\to {\Sigma }^{0}{K}^{+}$ and ${\Sigma }^{+}{K}_{S}^{0}$

Based on a sample of $4.\text{5}{\mathrm{fb}}^{-1}$ of ${e}^{+}{e}^{-}$ annihilation data collected in the energy region between 4.6 GeV and 4.7 GeV with the BESIII detector at BEPCII, two singly Cabibbo-suppressed decays ${\Lambda }_{c}^{+}\to {\Sigma }^{0}{K}^{+}$ and ${\Lambda }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}$ are studied. The ratio of the branching fraction $B\left({\Lambda }_{c}^{+}\to {\Sigma }^{0}{K}^{+}\right)$ relative to $B\left({\Lambda }_{c}^{+}\to {\Sigma }^{0}{\pi }^{+}\right)$ is measured to be $0.0361±0.0073\left(\mathrm{stat}.\right)±0.0005\left(\mathrm{syst}.\right)$, and the ratio of $B\left({\Lambda }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}\right)$ relative to $B\left({\Lambda }_{c}^{+}\to {\Sigma }^{+}{\pi }^{+}{\pi }^{-}\right)$ is measured to be $0.0106±0.0031\left(\mathrm{stat}.\right)±0.0004\left(\mathrm{syst}.\right)$. After taking the world-average branching fractions of the reference decay channels, the branching fractions $B\left({\Lambda }_{c}^{+}\to {\Sigma }^{0}{K}^{+}\right)$ and $B\left({\Lambda }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}\right)$ are determined to be $\left(4.7±0.9\left(\mathrm{stat}.\right)±0.1\left(\mathrm{syst}.\right)±0.3\left(\mathrm{ref}.\right)\right)×{10}^{-4}$ and $\left(4.8±1.4\left(\mathrm{stat}.\right)±0.2\left(\mathrm{syst}.\right)±0.3\left(\mathrm{ref}.\right)\right)×{10}^{-4}$, respectively. The branching fraction of the ${\Lambda }_{c}^{+}\to {\Sigma }^{+}{K}_{S}^{0}$ decay is measured for the first time.