Measurement of masses and branching ratios of $Ξ_c^+$ and $Ξ_c^0$ baryons

Abstract

We report a measurement of the $Ξ_c^+$ and $Ξ_c^0$ baryon masses, and the branching ratios for various $Ξ_c$ decays, using $140 \mathrm{fb}^{-1}$ of data collected by the Belle experiment at the KEKB $e^+ e^-$ collider.The mass splitting $m_{Ξ_c^0} - m_{Ξ_c^+}$ is found to be $2.9\pm 0.5 \mathrm{MeV}/c^2$; this measurement is three times as precise as the current world average. We measure the branching ratios $Γ(Ξ_c^+\to ΛKππ)/Γ(Ξ_c^+\toΞππ) = 0.32\pm 0.03 \pm 0.02$ and $Γ(Ξ_c^0\to p KKπ)/Γ(Ξ_c^0\toΞπ) = 0.33\pm 0.03 \pm 0.03$, with improved precision, and measure $Γ(Ξ_c^+\to p K^0_S K^0_S)/Γ(Ξ_c^+\toΞππ) = 0.087\pm 0.016 \pm 0.014$, $Γ(Ξ_c^0\to ΛKπ)/Γ(Ξ_c^0\toΞπ) = 1.07\pm 0.12 \pm 0.07$ and $Γ(Ξ_c^0\to ΛK^0_S)/Γ(Ξ_c^0\toΞπ) = 0.21\pm 0.02 \pm 0.02$ for the first time. In $Ξ_c^0$ decays to the $p K^- K^- π^+$ final state, we find evidence for the process $Ξ_c^0 \to p K^- \bar{K}{}^\ast(892)^0$ and measure the fraction of decays via this process to be $0.51\pm 0.03 \pm 0.01$.