Observations of the singly Cabibbo-suppressed decays \( {\Xi}_c^{+}\to p{K}_S^0 \), \( {\Xi}_c^{+}\to \Lambda {\pi}^{+} \), and \( {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} \) at Belle and Belle II

Using data samples of 983.0 fb⁻¹ and 427.9 fb⁻¹ accumulated with the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energy e⁺e⁻ colliders, singly Cabibbo-suppressed decays \( {\Xi}_c^{+}\to p{K}_S^0 \), \( {\Xi}_c^{+}\to \Lambda {\pi}^{+} \), and \( {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} \) are observed for the first time. The ratios of branching fractions of \( {\Xi}_c^{+}\to p{K}_S^0 \), \( {\Xi}_c^{+}\to \Lambda {\pi}^{+} \), and \( {\Xi}_c^{+}\to {\Sigma}^0{\pi}^{+} \) relative to that of \( {\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+} \) are measured to be

Multiplying these values by the branching fraction of the normalization channel, \( \mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right)=\left(2.9\pm 1.3\right)\% \), the absolute branching fractions are determined to be

The first and second uncertainties above are statistical and systematic, respectively, while the third ones arise from the uncertainty in \( \mathcal{B}\left({\Xi}_c^{+}\to {\Xi}^{-}{\pi}^{+}{\pi}^{+}\right) \).