Measurements of the branching fractions of $\hat{I}{ž}_c^{+}\to \hat{I}{\pounds }^{+}{K}_S^0$, $\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0\ddot{I}{€}^{+}$, and $\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0{K}^{+}$ at Belle and Belle II

Abstract

Using 983.0 ${\mathrm{fb}}^{-1}$ and 427.9 ${\mathrm{fb}}^{-1}$ data samples collected with the Belle and Belle II detectors at the KEKB and SuperKEKB asymmetric energy $e^{+}{e}^{-}$ colliders, respectively, we present studies of the Cabibbo-favored $\hat{I}{ž}_c^{+}$ decays $\hat{I}{ž}_c^{+}\to \hat{I}{\pounds }^{+}{K}_S^0$ and $\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0\ddot{I}{€}^{+}$, and the singly Cabibbo-suppressed decay $\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0{K}^{+}$. The ratios of branching fractions of $\hat{I}{ž}_c^{+}\to \hat{I}{\pounds }^{+}{K}_S^0$ and $\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0{K}^{+}$ relative to that of $\hat{I}{ž}_c^{+}\to \hat{I}{ž}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{+}$ are measured for the first time, while the ratio $\mathcal{B}(\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0\ddot{I}{€}^{+})/\mathcal{B}(\hat{I}{ž}_c^{+}\to \hat{I}{ž}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{+})$ is also determined and improved by an order of magnitude in precision. The measured branching fraction ratios are $\frac{\mathcal{B}(\hat{\mathcal{I}}{ž}_c^{+}\to \hat{\mathcal{I}}{\pounds }^{+}{\mathcal{K}}_{\mathcal{S}}^0)}{\mathcal{B}(\hat{\mathcal{I}}{ž}_c^{+}\to \hat{\mathcal{I}}{ž}^{-}\ddot{\mathcal{I}}{€}^{+}\ddot{\mathcal{I}}{€}^{+})}=0.067\pm 0.007\pm 0.003$, $\frac{\mathcal{B}(\hat{\mathcal{I}}{ž}_c^{+}\to \hat{\mathcal{I}}{ž}^0\ddot{\mathcal{I}}{€}^{+})}{\mathcal{B}(\hat{\mathcal{I}}{ž}_c^{+}\to \hat{\mathcal{I}}{ž}^{-}\ddot{\mathcal{I}}{€}^{+}\ddot{\mathcal{I}}{€}^{+})}=0.251\pm 0.005\pm 0.010$, $\frac{\mathcal{B}(\hat{\mathcal{I}}{ž}_c^{+}\to \hat{\mathcal{I}}{ž}^0{\mathcal{K}}^{+})}{\mathcal{B}(\hat{\mathcal{I}}{ž}_c^{+}\to \hat{\mathcal{I}}{ž}^{-}\ddot{\mathcal{I}}{€}^{+}\ddot{\mathcal{I}}{€}^{+})}=0.017\pm 0.003\pm 0.001$. Additionally, the ratio $\mathcal{B}(\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0{K}^{+})/\mathcal{B}(\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0\ddot{I}{€}^{+})$ is measured to be $0.068\pm 0.010\pm 0.004$. Here, the first and second uncertainties are statistical and systematic, respectively. Multiplying the ratios by the branching fraction of the normalization mode, $\mathcal{B}(\hat{I}{ž}_c^{+}\to \hat{I}{ž}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{+})=(2.9\pm 1.3)\%$, we obtain the following absolute branching fractions $\mathcal{B}(\hat{I}{ž}_c^{+}\to \hat{I}{\pounds }^{+}{K}_S^0)=(0.194\pm 0.021\pm 0.009\pm 0.087)$, $\mathcal{B}(\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0\ddot{I}{€}^{+})=(0.728\pm 0.014\pm 0.027\pm 0.326)$, $\mathcal{B}(\hat{I}{ž}_c^{+}\to \hat{I}{ž}^0{K}^{+})=(0.049\pm 0.007\pm 0.003\pm 0.022)$.

20 pages, 4 figures, 3 Tables; accepted for publication in JHEP