Search for CP violation in Ξ + c → Σ + h + h − and Λ + c → ph + h − at Belle II

We report decay-rate CP asymmetries of the singly-Cabibbo-suppressed decays Ξþc → Σ+h+h− and Λ+c → ph+h−, with h = K, π, measured using 428 fb−1 of e+e− collisions collected by the Belle II experiment at the SuperKEKB collider. The results, ACP(Ξ+c → Σ+K+K−) = (3.7 ± 6.6 ± 0.6)%, ACP(Ξ+c → Σ+π+π−) = (9.5 ± 6.8 ± 0.5)%, ACP(Λ+c → pK+K−) = (3.9 ± 1.7 ± 0.7)%, ACP(Λ+c → pπ+π−) = (0.3 ± 1.0 ± 0.2)%, where the first uncertainties are statistical and the second systematic, agree with CP symmetry. From these results we derive the sums ACP(Ξ+c → Σ+π+π−) + ACP(Λ+c → pK+K−) = (13.4 ± 7.0 ± 0.9)%, ACP(Ξ+c → Σ+KþK−) + ACP(Λ+c → pπ+π−) = (4.0± 6.6 ± 0.7)%, which are consistent with the U-spin symmetry prediction of zero. These are the first measurements of CP asymmetries for individual hadronic three-body charmed-baryon decays.